diff --git a/source/compiler/sc3.c b/source/compiler/sc3.c
index d717968..f7e15f6 100644
--- a/source/compiler/sc3.c
+++ b/source/compiler/sc3.c
@@ -2016,7 +2016,9 @@ static int nesting=0;
      * reserved memory block as a hidden parameter
      */
     retsize=(int)array_totalsize(symret);
-    assert(retsize>0);
+    if (retsize<=0) {
+      error(92,sym->name);
+    } /* if */
     modheap(retsize*sizeof(cell));/* address is in ALT */
     pushreg(sALT);                /* pass ALT as the last (hidden) parameter */
     decl_heap+=retsize;
diff --git a/source/compiler/sc5.c b/source/compiler/sc5.c
index 34a1c77..8f81319 100644
--- a/source/compiler/sc5.c
+++ b/source/compiler/sc5.c
@@ -128,7 +128,8 @@ static char *errmsg[] = {
 /*088*/  "public variables and local variables may not have states (symbol \"%s\")\n",
 /*089*/  "state variables may not be initialized (symbol \"%s\")\n",
 /*090*/  "public functions may not return arrays (symbol \"%s\")\n",
-/*091*/  "ambiguous constant; tag override is required (symbol \"%s\")\n"
+/*091*/  "ambiguous constant; tag override is required (symbol \"%s\")\n",
+/*092*/  "functions may not return arrays of unknown size (symbol \"%s\")\n"
 };
 
 static char *fatalmsg[] = {