diff --git a/GNUmakefile b/GNUmakefile
index 1f43b333bb..e69c1781f7 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -14,6 +14,7 @@ ifdef CONFIG
 	endif
 
 	XCODE_PATH ?= /Applications/Xcode.app
+	MACOSX_SDK ?= MacOSX10.13.sdk
 
 	include $(CONFIG)
 
diff --git a/vm/Config.macosx.x86.32 b/vm/Config.macosx.x86.32
index 68eaa9c0d1..d7e5edc6b8 100644
--- a/vm/Config.macosx.x86.32
+++ b/vm/Config.macosx.x86.32
@@ -1,6 +1,6 @@
 include vm/Config.macosx
 include vm/Config.x86.32
 
-# The last SDK to support x86
-CFLAGS += --sysroot=$(XCODE_PATH)/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk
-CXXFLAGS += --sysroot=$(XCODE_PATH)/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk
+# The last SDK to support x86 is 10.13
+CFLAGS += --sysroot=$(XCODE_PATH)/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$(MACOSX_SDK)
+CXXFLAGS += --sysroot=$(XCODE_PATH)/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/$(MACOSX_SDK)