Fix typo
diff --git a/Makefile b/Makefile
index f5d45f5..c850ec7 100644
--- a/Makefile
+++ b/Makefile
@@ -179,7 +179,7 @@
 LDFLAGS += $(LDFLAGS_$(CONFIG))
 
 ifdef EXTRA_DEFINES
-DEFINES += EXTRA_DEFINES
+DEFINES += $(EXTRA_DEFINES)
 endif
 
 CFLAGS += -std=c89 -pedantic