diff --git a/Makefile b/Makefile
index cdf2f24..305a07f 100644
--- a/Makefile
+++ b/Makefile
@@ -24,7 +24,7 @@ endif
 
 include $(MAKEFILE_COMMON)
 
-ifdef CURL
+ifneq (,$(CURL))
 CURL += -k
 endif