diff --git a/polymer/eduke32/build/src/build.c b/polymer/eduke32/build/src/build.c
index 48b47f4f2..ffae4f3a0 100644
--- a/polymer/eduke32/build/src/build.c
+++ b/polymer/eduke32/build/src/build.c
@@ -258,15 +258,16 @@ static int32_t osdcmd_vidmode(const osdfuncparm_t *parm)
 #ifdef USE_OPENGL
     case 1:	// bpp switch
         tmp = Batol(parm->parms[0]);
-        if (tmp==8 || tmp==16 || tmp==32)
-            newbpp = tmp;
-        break;
+        if (!(tmp==8 || tmp==16 || tmp==32))
+            return OSDCMD_SHOWHELP;
+        newbpp = tmp;
     case 4:	// fs, res, bpp switch
         newfullscreen = (Batol(parm->parms[3]) != 0);
     case 3:	// res & bpp switch
         tmp = Batol(parm->parms[2]);
-        if (tmp==8 || tmp==16 || tmp==32)
-            newbpp = tmp;
+        if (!(tmp==8 || tmp==16 || tmp==32))
+            return OSDCMD_SHOWHELP;
+        newbpp = tmp;
 #endif
     case 2: // res switch
         newx = Batol(parm->parms[0]);
diff --git a/polymer/eduke32/source/osdcmds.c b/polymer/eduke32/source/osdcmds.c
index d9fd27dc4..74868184c 100644
--- a/polymer/eduke32/source/osdcmds.c
+++ b/polymer/eduke32/source/osdcmds.c
@@ -371,12 +371,17 @@ static int32_t osdcmd_vidmode(const osdfuncparm_t *parm)
 {
     int32_t newbpp = ud.config.ScreenBPP, newwidth = ud.config.ScreenWidth,
             newheight = ud.config.ScreenHeight, newfs = ud.config.ScreenMode;
+    int32_t tmp;
+
     if (parm->numparms < 1 || parm->numparms > 4) return OSDCMD_SHOWHELP;
 
     switch (parm->numparms)
     {
     case 1: // bpp switch
-        newbpp = Batol(parm->parms[0]);
+        tmp = Batol(parm->parms[0]);
+        if (!(tmp==8 || tmp==16 || tmp==32))
+            return OSDCMD_SHOWHELP;
+        newbpp = tmp;
         break;
     case 2: // res switch
         newwidth = Batol(parm->parms[0]);
@@ -386,7 +391,10 @@ static int32_t osdcmd_vidmode(const osdfuncparm_t *parm)
     case 4:
         newwidth = Batol(parm->parms[0]);
         newheight = Batol(parm->parms[1]);
-        newbpp = Batol(parm->parms[2]);
+        tmp = Batol(parm->parms[2]);
+        if (!(tmp==8 || tmp==16 || tmp==32))
+            return OSDCMD_SHOWHELP;
+        newbpp = tmp;
         if (parm->numparms == 4)
             newfs = (Batol(parm->parms[3]) != 0);
         break;