diff --git a/Makefile b/Makefile
index 604696a1df4..a935df469c6 100644
--- a/Makefile
+++ b/Makefile
@@ -111,6 +111,7 @@ cross-compile-build-tools:
 	  cd BuildTools ; \
 	  unset CFLAGS ; \
 	  unset CXXFLAGS ; \
+	  unset SDKROOT ; \
 	  $(PROJ_SRC_DIR)/configure --build=$(BUILD_TRIPLE) \
 		--host=$(BUILD_TRIPLE) --target=$(BUILD_TRIPLE) \
 	        --disable-polly ; \