diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 3a1d919..0eb53f9 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -139,7 +139,8 @@
 int css_create_css_image(uint8_t cssid, bool default_image)
 {
     trace_css_new_image(cssid, default_image ? "(default)" : "");
-    if (cssid > MAX_CSSID) {
+    /* 255 is reserved */
+    if (cssid == 255) {
         return -EINVAL;
     }
     if (channel_subsys.css[cssid]) {
@@ -1226,7 +1227,7 @@
     uint8_t real_cssid;
 
     real_cssid = (!m && (cssid == 0)) ? channel_subsys.default_cssid : cssid;
-    if (real_cssid > MAX_CSSID || ssid > MAX_SSID ||
+    if (ssid > MAX_SSID ||
         !channel_subsys.css[real_cssid] ||
         !channel_subsys.css[real_cssid]->sch_set[ssid]) {
         return true;
@@ -1241,9 +1242,6 @@
     CssImage *css;
 
     trace_css_chpid_add(cssid, chpid, type);
-    if (cssid > MAX_CSSID) {
-        return -EINVAL;
-    }
     css = channel_subsys.css[cssid];
     if (!css) {
         return -EINVAL;
diff --git a/hw/s390x/css.h b/hw/s390x/css.h
index a320eea..fdcfa3a 100644
--- a/hw/s390x/css.h
+++ b/hw/s390x/css.h
@@ -19,7 +19,7 @@
 /* Channel subsystem constants. */
 #define MAX_SCHID 65535
 #define MAX_SSID 3
-#define MAX_CSSID 254 /* 255 is reserved */
+#define MAX_CSSID 255
 #define MAX_CHPID 255
 
 #define MAX_CIWS 62