diff --git Makefile.system Makefile.system
index 42ad498..d43aa7a 100644
--- Makefile.system
+++ Makefile.system
@@ -171,6 +171,7 @@ endif
 
 ifeq ($(NUM_THREADS), 1)
 override USE_THREAD = 0
+override USE_OPENMP = 0
 endif
 
 ifdef USE_THREAD
