diff --git a/src/w_wad.cpp b/src/w_wad.cpp
index f07b02bd1..80b2eb8b2 100644
--- a/src/w_wad.cpp
+++ b/src/w_wad.cpp
@@ -464,7 +464,7 @@ FUNCINLINE static ATTRINLINE UINT32 W_HashLumpName(const char *name, size_t len)
 {
 	char *uname = (char *)alloca(len + 1);
 	strlcpy(uname, name, len + 1);
-	strupr(uname);
+	strlwr(uname);
 	return HASH32(uname, len);
 }