diff --git a/polymer/eduke32/source/m32def.c b/polymer/eduke32/source/m32def.c
index f4f38fc9f..e52d74ac0 100644
--- a/polymer/eduke32/source/m32def.c
+++ b/polymer/eduke32/source/m32def.c
@@ -3741,7 +3741,7 @@ void C_Compile(const char *filenameortext, int32_t isfilename)
         fp = kopen4load(mptr, 0 /*g_loadFromGroupOnly*/);
         if (fp == -1) // JBF: was 0
         {
-            if (fs >= 4 && Bmemcmp(&mptr[fs-4], ".m32", 4) != 0)
+            if (fs < 4 || Bmemcmp(&mptr[fs-4], ".m32", 4) != 0)
             {
                 Bstrcat(&mptr[fs], ".m32");
                 fp = kopen4load(mptr, 0 /*g_loadFromGroupOnly*/);