diff --git a/src/Makefile b/src/Makefile
index fd07946..fef53af 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -681,6 +681,10 @@
 #LEAK_CFLAGS = -DEXITFREE
 #LEAK_LIBS = -lccmalloc
 
+# Uncomment this line to have Vim call abort() when an internal error is
+# detected.  Useful when using a tool to find errors.
+#ABORT_CLFAGS = -DABORT_ON_INTERNAL_ERROR
+
 #####################################################
 ###  Specific systems, check if yours is listed!  ### {{{
 #####################################################
@@ -1409,7 +1413,7 @@
 PRE_DEFS = -Iproto $(DEFS) $(GUI_DEFS) $(GUI_IPATH) $(CPPFLAGS) $(EXTRA_IPATHS)
 POST_DEFS = $(X_CFLAGS) $(MZSCHEME_CFLAGS) $(EXTRA_DEFS)
 
-ALL_CFLAGS = $(PRE_DEFS) $(CFLAGS) $(PROFILE_CFLAGS) $(SANITIZER_CFLAGS) $(LEAK_CFLAGS) $(POST_DEFS)
+ALL_CFLAGS = $(PRE_DEFS) $(CFLAGS) $(PROFILE_CFLAGS) $(SANITIZER_CFLAGS) $(LEAK_CFLAGS) $(ABORT_CLFAGS) $(POST_DEFS)
 
 # Exclude $CFLAGS for osdef.sh, for Mac 10.4 some flags don't work together
 # with "-E".
diff --git a/src/blowfish.c b/src/blowfish.c
index d3f5cff..ac9b088 100644
--- a/src/blowfish.c
+++ b/src/blowfish.c
@@ -426,7 +426,7 @@
     keylen = (int)STRLEN(key) / 2;
     if (keylen == 0)
     {
-	EMSG(_("E831: bf_key_init() called with empty password"));
+	IEMSG(_("E831: bf_key_init() called with empty password"));
 	return;
     }
     for (i = 0; i < keylen; i++)
diff --git a/src/dict.c b/src/dict.c
index 136348b..07d1000 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -214,7 +214,7 @@
 
     hi = hash_find(&dict->dv_hashtab, item->di_key);
     if (HASHITEM_EMPTY(hi))
-	EMSG2(_(e_intern2), "dictitem_remove()");
+	internal_error("dictitem_remove()");
     else
 	hash_remove(&dict->dv_hashtab, hi);
     dictitem_free(item);
diff --git a/src/edit.c b/src/edit.c
index 3a0e188..0d9e9d4 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -2299,7 +2299,7 @@
 	case CTRL_X_EVAL:
 	    return (c == Ctrl_P || c == Ctrl_N);
     }
-    EMSG(_(e_internal));
+    internal_error("vim_is_ctrl_x_key()");
     return FALSE;
 }
 
@@ -5431,7 +5431,7 @@
 	}
 	else
 	{
-	    EMSG2(_(e_intern2), "ins_complete()");
+	    internal_error("ins_complete()");
 	    return FAIL;
 	}
 
diff --git a/src/eval.c b/src/eval.c
index 18eb879..e92a97f 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -839,7 +839,7 @@
     {
 	hi = hash_find(&vimvarht, vimvars[idx].vv_di.di_key);
 	if (HASHITEM_EMPTY(hi))
-	    EMSG2(_(e_intern2), "restore_vimvar()");
+	    internal_error("restore_vimvar()");
 	else
 	    hash_remove(&vimvarht, hi);
     }
@@ -1308,7 +1308,7 @@
 	}
 	else if (*arg != ',' && *arg != ']')
 	{
-	    EMSG2(_(e_intern2), "ex_let_vars()");
+	    internal_error("ex_let_vars()");
 	    return FAIL;
 	}
     }
@@ -2830,7 +2830,7 @@
 	    }
 	    if (d == NULL)
 	    {
-		EMSG2(_(e_intern2), "do_unlet()");
+		internal_error("do_unlet()");
 		return FAIL;
 	    }
 	}
@@ -5678,7 +5678,7 @@
 	case VVAL_NONE:  return "v:none";
 	case VVAL_NULL:  return "v:null";
     }
-    EMSG2(_(e_intern2), "get_var_special_name()");
+    internal_error("get_var_special_name()");
     return "42";
 }
 
@@ -7152,7 +7152,7 @@
 	    break;
 #endif
 	case VAR_UNKNOWN:
-	    EMSG2(_(e_intern2), "get_tv_number(UNKNOWN)");
+	    internal_error("get_tv_number(UNKNOWN)");
 	    break;
     }
     if (denote == NULL)		/* useful for values that must be unsigned */
@@ -7199,7 +7199,7 @@
 	    break;
 # endif
 	case VAR_UNKNOWN:
-	    EMSG2(_(e_intern2), "get_tv_float(UNKNOWN)");
+	    internal_error("get_tv_float(UNKNOWN)");
 	    break;
     }
     return 0;
@@ -7733,7 +7733,7 @@
 		return;
 	    }
 	    else if (v->di_tv.v_type != tv->v_type)
-		EMSG2(_(e_intern2), "set_var()");
+		internal_error("set_var()");
 	}
 
 	clear_tv(&v->di_tv);
@@ -7962,7 +7962,7 @@
 	    }
 	    break;
 	case VAR_UNKNOWN:
-	    EMSG2(_(e_intern2), "copy_tv(UNKNOWN)");
+	    internal_error("copy_tv(UNKNOWN)");
 	    break;
     }
 }
@@ -8036,7 +8036,7 @@
 		ret = FAIL;
 	    break;
 	case VAR_UNKNOWN:
-	    EMSG2(_(e_intern2), "item_copy(UNKNOWN)");
+	    internal_error("item_copy(UNKNOWN)");
 	    ret = FAIL;
     }
     --recurse;
diff --git a/src/evalfunc.c b/src/evalfunc.c
index f643329..1257aa0 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2644,7 +2644,7 @@
 	    break;
 #endif
 	case VAR_UNKNOWN:
-	    EMSG2(_(e_intern2), "f_empty(UNKNOWN)");
+	    internal_error("f_empty(UNKNOWN)");
 	    n = TRUE;
 	    break;
     }
@@ -12695,7 +12695,7 @@
 	case VAR_JOB:     n = VAR_TYPE_JOB; break;
 	case VAR_CHANNEL: n = VAR_TYPE_CHANNEL; break;
 	case VAR_UNKNOWN:
-	     EMSG2(_(e_intern2), "f_type(UNKNOWN)");
+	     internal_error("f_type(UNKNOWN)");
 	     n = -1;
 	     break;
     }
diff --git a/src/ex_eval.c b/src/ex_eval.c
index daccfc8..7589f8e 100644
--- a/src/ex_eval.c
+++ b/src/ex_eval.c
@@ -595,7 +595,7 @@
 
     if (excp == NULL)
     {
-	EMSG(_(e_internal));
+	internal_error("discard_exception()");
 	return;
     }
 
@@ -700,7 +700,7 @@
 finish_exception(except_T *excp)
 {
     if (excp != caught_stack)
-	EMSG(_(e_internal));
+	internal_error("finish_exception()");
     caught_stack = caught_stack->caught;
     if (caught_stack != NULL)
     {
@@ -1603,7 +1603,7 @@
 	     * ":break", ":return", ":finish", error, interrupt, or another
 	     * exception. */
 	    if (cstack->cs_exception[cstack->cs_idx] != current_exception)
-		EMSG(_(e_internal));
+		internal_error("ex_catch()");
 	}
 	else
 	{
@@ -1737,7 +1737,7 @@
 		 * exception will be discarded. */
 		if (did_throw && cstack->cs_exception[cstack->cs_idx]
 							 != current_exception)
-		    EMSG(_(e_internal));
+		    internal_error("ex_finally()");
 	    }
 
 	    /*
diff --git a/src/getchar.c b/src/getchar.c
index 55db537..3657433 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -250,7 +250,7 @@
     }
     else if (buf->bh_curr == NULL)	/* buffer has already been read */
     {
-	EMSG(_("E222: Add to read buffer"));
+	IEMSG(_("E222: Add to read buffer"));
 	return;
     }
     else if (buf->bh_index != 0)
@@ -1321,11 +1321,11 @@
 free_typebuf(void)
 {
     if (typebuf.tb_buf == typebuf_init)
-	EMSG2(_(e_intern2), "Free typebuf 1");
+	internal_error("Free typebuf 1");
     else
 	vim_free(typebuf.tb_buf);
     if (typebuf.tb_noremap == noremapbuf_init)
-	EMSG2(_(e_intern2), "Free typebuf 2");
+	internal_error("Free typebuf 2");
     else
 	vim_free(typebuf.tb_noremap);
 }
@@ -4868,7 +4868,7 @@
 			c1 = 'l';
 			break;
 		    default:
-			EMSG(_("E228: makemap: Illegal mode"));
+			IEMSG(_("E228: makemap: Illegal mode"));
 			return FAIL;
 		}
 		do	/* do this twice if c2 is set, 3 times with c3 */
diff --git a/src/globals.h b/src/globals.h
index fea9543..c15e4f9 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1440,6 +1440,7 @@
 EXTERN char_u e_fontwidth[]	INIT(= N_("E236: Font \"%s\" is not fixed-width"));
 #endif
 EXTERN char_u e_internal[]	INIT(= N_("E473: Internal error"));
+EXTERN char_u e_intern2[]	INIT(= N_("E685: Internal error: %s"));
 EXTERN char_u e_interr[]	INIT(= N_("Interrupted"));
 EXTERN char_u e_invaddr[]	INIT(= N_("E14: Invalid address"));
 EXTERN char_u e_invarg[]	INIT(= N_("E474: Invalid argument"));
@@ -1589,7 +1590,6 @@
 EXTERN char_u e_guarded[]	INIT(= N_("E463: Region is guarded, cannot modify"));
 EXTERN char_u e_nbreadonly[]	INIT(= N_("E744: NetBeans does not allow changes in read-only files"));
 #endif
-EXTERN char_u e_intern2[]	INIT(= N_("E685: Internal error: %s"));
 EXTERN char_u e_maxmempat[]	INIT(= N_("E363: pattern uses more memory than 'maxmempattern'"));
 EXTERN char_u e_emptybuf[]	INIT(= N_("E749: empty buffer"));
 EXTERN char_u e_nobufnr[]	INIT(= N_("E86: Buffer %ld does not exist"));
diff --git a/src/gui_beval.c b/src/gui_beval.c
index 4a7c06e..8569f60 100644
--- a/src/gui_beval.c
+++ b/src/gui_beval.c
@@ -218,7 +218,7 @@
 
     if (mesg != NULL && mesgCB != NULL)
     {
-	EMSG(_("E232: Cannot create BalloonEval with both message and callback"));
+	IEMSG(_("E232: Cannot create BalloonEval with both message and callback"));
 	return NULL;
     }
 
diff --git a/src/gui_w32.c b/src/gui_w32.c
index be2158d..02c5ed1 100644
--- a/src/gui_w32.c
+++ b/src/gui_w32.c
@@ -8620,7 +8620,7 @@
 
     if (mesg != NULL && mesgCB != NULL)
     {
-	EMSG(_("E232: Cannot create BalloonEval with both message and callback"));
+	IEMSG(_("E232: Cannot create BalloonEval with both message and callback"));
 	return NULL;
     }
 
diff --git a/src/hangulin.c b/src/hangulin.c
index 1b5604b..60b3577 100644
--- a/src/hangulin.c
+++ b/src/hangulin.c
@@ -590,7 +590,7 @@
 	    return AUTOMATA_CORRECT_NEW;
 
 	default:
-	    EMSG(_("E256: Hangul automata ERROR"));
+	    IEMSG(_("E256: Hangul automata ERROR"));
 	    break;
     }
     return AUTOMATA_ERROR; /* RrEeAaLlLlYy EeRrRrOoRr */
diff --git a/src/hashtab.c b/src/hashtab.c
index d8d3aed..658bfb9 100644
--- a/src/hashtab.c
+++ b/src/hashtab.c
@@ -210,7 +210,7 @@
     hi = hash_lookup(ht, key, hash);
     if (!HASHITEM_EMPTY(hi))
     {
-	EMSG2(_(e_intern2), "hash_add()");
+	internal_error("hash_add()");
 	return FAIL;
     }
     return hash_add_item(ht, hi, key, hash);
diff --git a/src/if_cscope.c b/src/if_cscope.c
index 9e7a362..ce6b87f 100644
--- a/src/if_cscope.c
+++ b/src/if_cscope.c
@@ -1792,7 +1792,7 @@
 	cs_print_tags_priv(mp, cp, cnt);
 	break;
     default:	/* should not reach here */
-	(void)EMSG(_("E570: fatal error in cs_manage_matches"));
+	IEMSG(_("E570: fatal error in cs_manage_matches"));
 	return NULL;
     }
 
diff --git a/src/json.c b/src/json.c
index 36d47aa..4ec4411 100644
--- a/src/json.c
+++ b/src/json.c
@@ -328,7 +328,7 @@
 	    break;
 #endif
 	case VAR_UNKNOWN:
-	    EMSG2(_(e_intern2), "json_encode_item()");
+	    internal_error("json_encode_item()");
 	    return FAIL;
     }
     return OK;
diff --git a/src/memfile.c b/src/memfile.c
index 2f75201..0fb2787 100644
--- a/src/memfile.c
+++ b/src/memfile.c
@@ -482,7 +482,7 @@
     flags = hp->bh_flags;
 
     if ((flags & BH_LOCKED) == 0)
-	EMSG(_("E293: block was not locked"));
+	IEMSG(_("E293: block was not locked"));
     flags &= ~BH_LOCKED;
     if (dirty)
     {
diff --git a/src/memline.c b/src/memline.c
index 37555e6..e3a4bdb 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -333,7 +333,7 @@
 	goto error;
     if (hp->bh_bnum != 0)
     {
-	EMSG(_("E298: Didn't get block nr 0?"));
+	IEMSG(_("E298: Didn't get block nr 0?"));
 	goto error;
     }
     b0p = (ZERO_BL *)(hp->bh_data);
@@ -383,7 +383,7 @@
 	goto error;
     if (hp->bh_bnum != 1)
     {
-	EMSG(_("E298: Didn't get block nr 1?"));
+	IEMSG(_("E298: Didn't get block nr 1?"));
 	goto error;
     }
     pp = (PTR_BL *)(hp->bh_data);
@@ -401,7 +401,7 @@
 	goto error;
     if (hp->bh_bnum != 2)
     {
-	EMSG(_("E298: Didn't get block nr 2?"));
+	IEMSG(_("E298: Didn't get block nr 2?"));
 	goto error;
     }
 
@@ -950,7 +950,7 @@
 
     b0p = (ZERO_BL *)(hp->bh_data);
     if (ml_check_b0_id(b0p) == FAIL)
-	EMSG(_("E304: ml_upd_block0(): Didn't get block 0??"));
+	IEMSG(_("E304: ml_upd_block0(): Didn't get block 0??"));
     else
     {
 	if (what == UB_FNAME)
@@ -2450,7 +2450,7 @@
 	    /* Avoid giving this message for a recursive call, may happen when
 	     * the GUI redraws part of the text. */
 	    ++recursive;
-	    EMSGN(_("E315: ml_get: invalid lnum: %ld"), lnum);
+	    IEMSGN(_("E315: ml_get: invalid lnum: %ld"), lnum);
 	    --recursive;
 	}
 errorret:
@@ -2485,7 +2485,7 @@
 		/* Avoid giving this message for a recursive call, may happen
 		 * when the GUI redraws part of the text. */
 		++recursive;
-		EMSGN(_("E316: ml_get: cannot find line %ld"), lnum);
+		IEMSGN(_("E316: ml_get: cannot find line %ld"), lnum);
 		--recursive;
 	    }
 	    goto errorret;
@@ -2900,7 +2900,7 @@
 	    pp = (PTR_BL *)(hp->bh_data);   /* must be pointer block */
 	    if (pp->pb_id != PTR_ID)
 	    {
-		EMSG(_("E317: pointer block id wrong 3"));
+		IEMSG(_("E317: pointer block id wrong 3"));
 		mf_put(mfp, hp, FALSE, FALSE);
 		return FAIL;
 	    }
@@ -3042,7 +3042,7 @@
 	 */
 	if (stack_idx < 0)
 	{
-	    EMSG(_("E318: Updated too many blocks?"));
+	    IEMSG(_("E318: Updated too many blocks?"));
 	    buf->b_ml.ml_stack_top = 0;	/* invalidate stack */
 	}
     }
@@ -3220,7 +3220,7 @@
 	    pp = (PTR_BL *)(hp->bh_data);   /* must be pointer block */
 	    if (pp->pb_id != PTR_ID)
 	    {
-		EMSG(_("E317: pointer block id wrong 4"));
+		IEMSG(_("E317: pointer block id wrong 4"));
 		mf_put(mfp, hp, FALSE, FALSE);
 		return FAIL;
 	    }
@@ -3432,7 +3432,7 @@
 
 	hp = ml_find_line(buf, lnum, ML_FIND);
 	if (hp == NULL)
-	    EMSGN(_("E320: Cannot find line %ld"), lnum);
+	    IEMSGN(_("E320: Cannot find line %ld"), lnum);
 	else
 	{
 	    dp = (DATA_BL *)(hp->bh_data);
@@ -3674,7 +3674,7 @@
 	pp = (PTR_BL *)(dp);		/* must be pointer block */
 	if (pp->pb_id != PTR_ID)
 	{
-	    EMSG(_("E317: pointer block id wrong"));
+	    IEMSG(_("E317: pointer block id wrong"));
 	    goto error_block;
 	}
 
@@ -3719,11 +3719,11 @@
 	if (idx >= (int)pp->pb_count)	    /* past the end: something wrong! */
 	{
 	    if (lnum > buf->b_ml.ml_line_count)
-		EMSGN(_("E322: line number out of range: %ld past the end"),
+		IEMSGN(_("E322: line number out of range: %ld past the end"),
 					      lnum - buf->b_ml.ml_line_count);
 
 	    else
-		EMSGN(_("E323: line count wrong in block %ld"), bnum);
+		IEMSGN(_("E323: line count wrong in block %ld"), bnum);
 	    goto error_block;
 	}
 	if (action == ML_DELETE)
@@ -3817,7 +3817,7 @@
 	if (pp->pb_id != PTR_ID)
 	{
 	    mf_put(mfp, hp, FALSE, FALSE);
-	    EMSG(_("E317: pointer block id wrong 2"));
+	    IEMSG(_("E317: pointer block id wrong 2"));
 	    break;
 	}
 	pp->pb_pointer[ip->ip_index].pe_line_count += count;
diff --git a/src/message.c b/src/message.c
index f8152a7..32360a9 100644
--- a/src/message.c
+++ b/src/message.c
@@ -662,6 +662,7 @@
     return msg_attr(s, attr);
 }
 
+
 /*
  * Print an error message with one "%s" and one string argument.
  */
@@ -671,6 +672,84 @@
     return emsg3(s, a1, NULL);
 }
 
+/*
+ * Print an error message with one or two "%s" and one or two string arguments.
+ * This is not in message.c to avoid a warning for prototypes.
+ */
+    int
+emsg3(char_u *s, char_u *a1, char_u *a2)
+{
+    if (emsg_not_now())
+	return TRUE;		/* no error messages at the moment */
+    vim_snprintf((char *)IObuff, IOSIZE, (char *)s, a1, a2);
+    return emsg(IObuff);
+}
+
+/*
+ * Print an error message with one "%ld" and one long int argument.
+ * This is not in message.c to avoid a warning for prototypes.
+ */
+    int
+emsgn(char_u *s, long n)
+{
+    if (emsg_not_now())
+	return TRUE;		/* no error messages at the moment */
+    vim_snprintf((char *)IObuff, IOSIZE, (char *)s, n);
+    return emsg(IObuff);
+}
+
+/*
+ * Same as emsg(...), but abort on error when ABORT_ON_INTERNAL_ERROR is
+ * defined. It is used for internal errors only, so that they can be
+ * detected when fuzzing vim.
+ */
+    void
+iemsg(char_u *s)
+{
+    msg(s);
+#ifdef ABORT_ON_INTERNAL_ERROR
+    abort();
+#endif
+}
+
+
+/*
+ * Same as emsg2(...) but abort on error when ABORT_ON_INTERNAL_ERROR is
+ * defined. It is used for internal errors only, so that they can be
+ * detected when fuzzing vim.
+ */
+    void
+iemsg2(char_u *s, char_u *a1)
+{
+    emsg2(s, a1);
+#ifdef ABORT_ON_INTERNAL_ERROR
+    abort();
+#endif
+}
+
+/*
+ * Same as emsgn(...) but abort on error when ABORT_ON_INTERNAL_ERROR is
+ * defined. It is used for internal errors only, so that they can be
+ * detected when fuzzing vim.
+ */
+    void
+iemsgn(char_u *s, long n)
+{
+    emsgn(s, n);
+#ifdef ABORT_ON_INTERNAL_ERROR
+    abort();
+#endif
+}
+
+/*
+ * Give an "Internal error" message.
+ */
+    void
+internal_error(char *where)
+{
+    IEMSG2(_(e_intern2), where);
+}
+
 /* emsg3() and emsgn() are in misc2.c to avoid warnings for the prototypes. */
 
     void
diff --git a/src/misc2.c b/src/misc2.c
index 3803249..27d26be 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -918,7 +918,7 @@
     {
 	/* Don't hide this message */
 	emsg_silent = 0;
-	EMSGN(_("E341: Internal error: lalloc(%ld, )"), size);
+	IEMSGN(_("E341: Internal error: lalloc(%ld, )"), size);
 	return NULL;
     }
 
@@ -1075,7 +1075,7 @@
     p_ea = FALSE;
     if (first_tabpage->tp_next != NULL)
 	do_cmdline_cmd((char_u *)"tabonly!");
-    if (firstwin != lastwin)
+    if (!ONE_WINDOW)
 	do_cmdline_cmd((char_u *)"only!");
 # endif
 
@@ -6040,32 +6040,6 @@
 }
 #endif
 
-/*
- * Print an error message with one or two "%s" and one or two string arguments.
- * This is not in message.c to avoid a warning for prototypes.
- */
-    int
-emsg3(char_u *s, char_u *a1, char_u *a2)
-{
-    if (emsg_not_now())
-	return TRUE;		/* no error messages at the moment */
-    vim_snprintf((char *)IObuff, IOSIZE, (char *)s, a1, a2);
-    return emsg(IObuff);
-}
-
-/*
- * Print an error message with one "%ld" and one long int argument.
- * This is not in message.c to avoid a warning for prototypes.
- */
-    int
-emsgn(char_u *s, long n)
-{
-    if (emsg_not_now())
-	return TRUE;		/* no error messages at the moment */
-    vim_snprintf((char *)IObuff, IOSIZE, (char *)s, n);
-    return emsg(IObuff);
-}
-
 #if defined(FEAT_SPELL) || defined(FEAT_PERSISTENT_UNDO) || defined(PROTO)
 /*
  * Read 2 bytes from "fd" and turn them into an int, MSB first.
diff --git a/src/option.c b/src/option.c
index ecfdc40..2b9ba2d 100644
--- a/src/option.c
+++ b/src/option.c
@@ -5615,7 +5615,7 @@
 	flagp = insecure_flag(idx, opt_flags);
 	return (*flagp & P_INSECURE) != 0;
     }
-    EMSG2(_(e_intern2), "was_set_insecurely()");
+    internal_error("was_set_insecurely()");
     return -1;
 }
 
@@ -5696,7 +5696,7 @@
 	if (idx < 0)	/* not found (should not happen) */
 	{
 	    EMSG2(_(e_intern2), "set_string_option_direct()");
-	    EMSG2(_("For option %s"), name);
+	    IEMSG2(_("For option %s"), name);
 	    return;
 	}
     }
@@ -9375,7 +9375,7 @@
 		    ret = NULL;
 		break;
 	    default:
-		EMSG2(_(e_intern2), "option_iter_next()");
+		internal_error("option_iter_next()");
 		return NULL;
 	}
     }
@@ -10496,7 +10496,7 @@
 #ifdef FEAT_SIGNS
 	case PV_SCL:	return (char_u *)&(curwin->w_p_scl);
 #endif
-	default:	EMSG(_("E356: get_varp ERROR"));
+	default:	IEMSG(_("E356: get_varp ERROR"));
     }
     /* always return a valid pointer to avoid a crash! */
     return (char_u *)&(curbuf->b_p_wm);
diff --git a/src/proto/message.pro b/src/proto/message.pro
index 7112b09..c9d62c6 100644
--- a/src/proto/message.pro
+++ b/src/proto/message.pro
@@ -11,6 +11,12 @@
 void do_perror(char *msg);
 int emsg(char_u *s);
 int emsg2(char_u *s, char_u *a1);
+int emsg3(char_u *s, char_u *a1, char_u *a2);
+int emsgn(char_u *s, long n);
+void iemsg(char_u *s);
+void iemsg2(char_u *s, char_u *a1);
+void iemsgn(char_u *s, long n);
+void internal_error(char *where);
 void emsg_invreg(int name);
 char_u *msg_trunc_attr(char_u *s, int force, int attr);
 char_u *msg_may_trunc(int force, char_u *s);
diff --git a/src/proto/misc2.pro b/src/proto/misc2.pro
index d18ae20..144324f 100644
--- a/src/proto/misc2.pro
+++ b/src/proto/misc2.pro
@@ -99,8 +99,6 @@
 void sort_strings(char_u **files, int count);
 int pathcmp(const char *p, const char *q, int maxlen);
 int filewritable(char_u *fname);
-int emsg3(char_u *s, char_u *a1, char_u *a2);
-int emsgn(char_u *s, long n);
 int get2c(FILE *fd);
 int get3c(FILE *fd);
 int get4c(FILE *fd);
diff --git a/src/quickfix.c b/src/quickfix.c
index a45faea..a563fa9 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -3231,7 +3231,7 @@
     {
 	if (buf != curbuf)
 	{
-	    EMSG2(_(e_intern2), "qf_fill_buffer()");
+	    internal_error("qf_fill_buffer()");
 	    return;
 	}
 
diff --git a/src/regexp.c b/src/regexp.c
index 8d63d5a..78d6431 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -335,11 +335,13 @@
 /* Used for an error (down from) vim_regcomp(): give the error message, set
  * rc_did_emsg and return NULL */
 #define EMSG_RET_NULL(m) return (EMSG(m), rc_did_emsg = TRUE, (void *)NULL)
+#define IEMSG_RET_NULL(m) return (IEMSG(m), rc_did_emsg = TRUE, (void *)NULL)
 #define EMSG_RET_FAIL(m) return (EMSG(m), rc_did_emsg = TRUE, FAIL)
 #define EMSG2_RET_NULL(m, c) return (EMSG2((m), (c) ? "" : "\\"), rc_did_emsg = TRUE, (void *)NULL)
 #define EMSG2_RET_FAIL(m, c) return (EMSG2((m), (c) ? "" : "\\"), rc_did_emsg = TRUE, FAIL)
 #define EMSG_ONE_RET_NULL EMSG2_RET_NULL(_("E369: invalid item in %s%%[]"), reg_magic == MAGIC_ALL)
 
+
 #define MAX_LIMIT	(32767L << 16L)
 
 static int re_multi_type(int);
@@ -2043,7 +2045,7 @@
       case Magic(')'):
 	if (one_exactly)
 	    EMSG_ONE_RET_NULL;
-	EMSG_RET_NULL(_(e_internal));	/* Supposed to be caught earlier. */
+	IEMSG_RET_NULL(_(e_internal));	/* Supposed to be caught earlier. */
 	/* NOTREACHED */
 
       case Magic('='):
@@ -5070,7 +5072,7 @@
 		}
 		else
 		{
-		    EMSG(_(e_internal));	    /* Shouldn't happen */
+		    internal_error("BRACE_LIMITS");
 		    status = RA_FAIL;
 		}
 	    }
diff --git a/src/spell.c b/src/spell.c
index eb81ad2..91a48fa 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -6428,7 +6428,7 @@
     sfwordnr = soundfold_find(slang, goodword);
     if (sfwordnr < 0)
     {
-	EMSG2(_(e_intern2), "add_sound_suggest()");
+	internal_error("add_sound_suggest()");
 	return;
     }
 
diff --git a/src/undo.c b/src/undo.c
index cc74edd..57c3c20 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -2582,7 +2582,7 @@
 	    if (uhp == NULL || uhp->uh_walk != mark)
 	    {
 		/* Need to redo more but can't find it... */
-		EMSG2(_(e_intern2), "undo_time()");
+		internal_error("undo_time()");
 		break;
 	    }
 	}
@@ -2654,7 +2654,7 @@
 #ifdef FEAT_AUTOCMD
 	    unblock_autocmds();
 #endif
-	    EMSG(_("E438: u_undo: line numbers wrong"));
+	    IEMSG(_("E438: u_undo: line numbers wrong"));
 	    changed();		/* don't want UNCHANGED now */
 	    return;
 	}
@@ -3234,7 +3234,7 @@
 {
     if (curbuf->b_u_newhead == NULL || curbuf->b_u_newhead->uh_entry == NULL)
     {
-	EMSG(_("E439: undo list corrupt"));
+	IEMSG(_("E439: undo list corrupt"));
 	return NULL;
     }
     return curbuf->b_u_newhead->uh_entry;
@@ -3266,7 +3266,7 @@
 	uep->ue_bot = uep->ue_top + uep->ue_size + 1 + extra;
 	if (uep->ue_bot < 1 || uep->ue_bot > curbuf->b_ml.ml_line_count)
 	{
-	    EMSG(_("E440: undo line missing"));
+	    IEMSG(_("E440: undo line missing"));
 	    uep->ue_bot = uep->ue_top + 1;  /* assume all lines deleted, will
 					     * get all the old lines back
 					     * without deleting the current
diff --git a/src/userfunc.c b/src/userfunc.c
index c75ccbc..369d92a 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2771,7 +2771,7 @@
 #ifdef EXITFREE
 	if (!entered_free_all_mem)
 #endif
-	    EMSG2(_(e_intern2), "func_unref()");
+	    internal_error("func_unref()");
     }
     if (fp != NULL && --fp->uf_refcount <= 0)
     {
@@ -2814,7 +2814,7 @@
     else if (isdigit(*name))
 	/* Only give an error for a numbered function.
 	 * Fail silently, when named or lambda function isn't found. */
-	EMSG2(_(e_intern2), "func_ref()");
+	internal_error("func_ref()");
 }
 
 /*
diff --git a/src/version.c b/src/version.c
index 6d12500..80e30dc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    74,
+/**/
     73,
 /**/
     72,
diff --git a/src/vim.h b/src/vim.h
index 5946d63..eec3e4f 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1623,6 +1623,9 @@
 #define EMSG3(s, p, q)		    emsg3((char_u *)(s), (char_u *)(p), (char_u *)(q))
 #define EMSGN(s, n)		    emsgn((char_u *)(s), (long)(n))
 #define EMSGU(s, n)		    emsgu((char_u *)(s), (long_u)(n))
+#define IEMSG(s)		    iemsg((char_u *)(s))
+#define IEMSG2(s, p)		    iemsg2((char_u *)(s), (char_u *)(p))
+#define IEMSGN(s, n)		    iemsgn((char_u *)(s), (long)(n))
 #define OUT_STR(s)		    out_str((char_u *)(s))
 #define OUT_STR_NF(s)		    out_str_nf((char_u *)(s))
 #define MSG_PUTS(s)		    msg_puts((char_u *)(s))
diff --git a/src/window.c b/src/window.c
index c4448b7..8e53368 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2538,7 +2538,7 @@
 		;
 	    if (ptp == NULL)
 	    {
-		EMSG2(_(e_intern2), "win_close_othertab()");
+		internal_error("win_close_othertab()");
 		return;
 	    }
 	    ptp->tp_next = tp->tp_next;