diff --git a/source/duke3d/src/gamedef.cpp b/source/duke3d/src/gamedef.cpp
index d4e8a3424..98bf8be49 100644
--- a/source/duke3d/src/gamedef.cpp
+++ b/source/duke3d/src/gamedef.cpp
@@ -613,7 +613,7 @@ char const * VM_GetKeywordForID(int32_t id)
         if (keyword.val == id)
             return keyword.token;
 
-    return nullptr;
+    return "<invalid keyword>";
 }
 #endif