diff --git a/Makefile.system b/Makefile.system
index 972238f36..5caad0b03 100644
--- a/Makefile.system
+++ b/Makefile.system
@@ -181,6 +181,7 @@ endif
 
 ifeq ($(NUM_THREADS), 1)
 override USE_THREAD = 0
+override USE_OPENMP = 0
 endif
 
 ifdef USE_THREAD