diff --git a/Makefile b/Makefile
index 9ba2b1a..e0c7b49 100644
--- a/Makefile
+++ b/Makefile
@@ -5,18 +5,18 @@ OBJS = $(subst .cpp,.o, $(SRCS))
 
 MODULE_big = stringtheory
 
-PG_CPPFLAGS = -O3 -std=c++17 -I src/sse
+PG_CXXFLAGS = -O3 -std=c++17 -I src/sse
 
 UNAME_S := $(shell uname -m)
 ifeq ($(UNAME_S),arm64)
-	PG_CPPFLAGS += -stdlib=libc++ -DHAVE_NEON_INSTRUCTIONS=1
+	PG_CXXFLAGS += -stdlib=libc++ -DHAVE_NEON_INSTRUCTIONS=1
 endif
 ifeq ($(UNAME_S),aarch64)
 	PG_CPPFLAGS += -DHAVE_NEON_INSTRUCTIONS=1
 endif
 ifeq ($(UNAME_S),x86_64)
 	SHLIB_LINK += -lrt -std=c++17 -msse4.2
-	PG_CPPFLAGS += -msse4.2
+	PG_CXXFLAGS += -msse4.2
 endif
 
 EXTENSION = stringtheory