diff --git a/GNUmakefile b/GNUmakefile
index a0bfa87..bb90699 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -86,5 +86,10 @@ ifneq ($(findstring gcc, $(CC)),)
 libobjc_CFLAGS += -fgnu89-inline 
 endif
 
+# Hack to get the __sync_* GCC builtins to work on Windows
+ifeq ($(GNUSTEP_TARGET_OS), mingw32)
+libobjc_CFLAGS += -march=i586
+endif
+
 include $(GNUSTEP_MAKEFILES)/aggregate.make
 include $(GNUSTEP_MAKEFILES)/library.make
diff --git a/toydispatch/GNUmakefile b/toydispatch/GNUmakefile
index 2f5fcc4..39af68e 100644
--- a/toydispatch/GNUmakefile
+++ b/toydispatch/GNUmakefile
@@ -15,4 +15,9 @@ toydispatch_LIBRARIES_DEPEND_UPON += -lpthread
 
 toydispatch_CFLAGS += -Werror -std=c99
 
+# Hack to get the __sync_* GCC builtins to work on Windows
+ifeq ($(GNUSTEP_TARGET_OS), mingw32)
+toydispatch_CFLAGS += -march=i586
+endif
+
 include $(GNUSTEP_MAKEFILES)/library.make