diff --git a/Makefile.system b/Makefile.system
index 44eacda4b..c24647d62 100644
--- a/Makefile.system
+++ b/Makefile.system
@@ -1070,7 +1070,7 @@ ifdef USE_SIMPLE_THREADED_LEVEL3
 CCOMMON_OPT	+= -DUSE_SIMPLE_THREADED_LEVEL3
 endif
 
-ifdef USE_TLS
+ifeq ($(USE_TLS), 1)
 CCOMMON_OPT += -DUSE_TLS
 endif