--- a/Tools/Makefile.preamble
+++ b/Tools/Makefile.preamble
@@ -45,7 +45,7 @@ endif
 #ADDITIONAL_OBJCFLAGS +=
 
 # Additional flags to pass to the C compiler
-#ADDITIONAL_CFLAGS += 
+ADDITIONAL_CFLAGS += -std=gnu17
 
 # Additional include directories the compiler should search
 ADDITIONAL_INCLUDE_DIRS += -I../Source/$(GNUSTEP_TARGET_DIR) -I../Source/