diff --git a/Makefile b/Makefile
index 0ac20d971713..b54df174acde 100644
--- a/Makefile
+++ b/Makefile
@@ -190,6 +190,7 @@ endif
 
 ifeq ($(USE_OPENMP), 1)
 	CFLAGS += -fopenmp
+	CFLAGS += -DMXNET_USE_OPENMP=1
 endif
 
 ifeq ($(USE_NNPACK), 1)