diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index e6609fe..4d2fc87 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -112,7 +112,7 @@
 BL31_SOURCES		+=	lib/extensions/mpam/mpam.c
 endif
 
-ifeq (${ENABLE_TRBE_FOR_NS},1)
+ifneq (${ENABLE_TRBE_FOR_NS},0)
 BL31_SOURCES		+=	lib/extensions/trbe/trbe.c
 endif