diff --git a/src/p_djgpp2.cpp b/src/p_djgpp2.cpp
index 52eecc8d..c77cb769 100644
--- a/src/p_djgpp2.cpp
+++ b/src/p_djgpp2.cpp
@@ -80,6 +80,7 @@ int PackDjgpp2::buildLoader(const Filter *ft)
              );
     if (ft->id)
     {
+        assert(ft->calls > 0);
         addLoader("DJCALLT2",NULL);
         addFilter32(ft->id);
     }