diff --git a/Makefile b/Makefile
index 631bff9..6f39688 100644
--- a/Makefile
+++ b/Makefile
@@ -50,6 +50,10 @@ EXTENSION_FLAGS=\
 
 BUILD_FLAGS=-DEXTENSION_STATIC_BUILD=1 -DBUILD_EXTENSIONS="tpch" ${OSX_BUILD_FLAG} -DDUCKDB_EXPLICIT_PLATFORM='${DUCKDB_PLATFORM}'
 
+ifeq ($(DUCKDB_PLATFORM_RTOOLS),1)
+	BUILD_FLAGS:=${BUILD_FLAGS} -DCMAKE_CXX_FLAGS="-DDUCKDB_PLATFORM_RTOOLS=1"
+endif
+
 CLIENT_FLAGS :=
 pull:
 	git submodule init