diff --git a/src/console/c_cvars.cpp b/src/console/c_cvars.cpp
index 2bc81c7c9..978a6da55 100644
--- a/src/console/c_cvars.cpp
+++ b/src/console/c_cvars.cpp
@@ -1756,6 +1756,10 @@ void C_GrabCVarDefaults ()
 
 	while ((lump = Wads.FindLump("DEFCVARS", &lastlump)) != -1)
 	{
+		// don't parse from wads
+		if (lastlump > Wads.GetLastLump(Wads.GetMaxIwadNum()))
+			I_FatalError("Cannot load DEFCVARS from a wadfile!\n");
+
 		FScanner sc(lump);
 
 		sc.MustGetString();