diff --git a/Makefile b/Makefile
index 3fd68d1d..cd4afa61 100644
--- a/Makefile
+++ b/Makefile
@@ -404,7 +404,7 @@ LIBRARY_DIRS += $(LIB_BUILD_DIR)
 CXXFLAGS += -MMD -MP
 
 # Complete build flags.
-COMMON_FLAGS += $(foreach includedir,$(INCLUDE_DIRS),-isystem $(includedir))
+COMMON_FLAGS += $(foreach includedir,$(INCLUDE_DIRS),-I$(includedir))
 CXXFLAGS += -pthread -fPIC $(COMMON_FLAGS) $(WARNINGS)
 NVCCFLAGS += -ccbin=$(CXX) -Xcompiler -fPIC $(COMMON_FLAGS)
 # mex may invoke an older gcc that is too liberal with -Wuninitalized