diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 3491811..e308c79 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -2922,6 +2922,8 @@
         unsigned long uriHash = hash_secret_salt;
         ((XML_Char *)s)[-1] = 0;  /* clear flag */
         id = (ATTRIBUTE_ID *)lookup(parser, &dtd->attributeIds, s, 0);
+        if (!id || !id->prefix)
+          return XML_ERROR_NO_MEMORY;
         b = id->prefix->binding;
         if (!b)
           return XML_ERROR_UNBOUND_PREFIX;
@@ -5486,6 +5488,8 @@
             return NULL;
           id->prefix = (PREFIX *)lookup(parser, &dtd->prefixes, poolStart(&dtd->pool),
                                         sizeof(PREFIX));
+          if (!id->prefix)
+            return NULL;
           if (id->prefix->name == poolStart(&dtd->pool))
             poolFinish(&dtd->pool);
           else