diff --git a/Makefile b/Makefile
index d382e707..c00d707d 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@ LIBS += -liconv
 	endif
 endif
 
-FILENAME ?= FILENAME_DEF
+FILENAME ?= $(FILENAME_DEF)
 
 ifeq ($(FIX_BUGS), 1)
 CXXFLAGS += -DFIX_BUGS