-MACOS_DEPLOYMENT_VERSION = @MACOS_DEPLOYMENT_VERSION@
-MACOS_DEPLOYMENT_SDK = @MACOS_DEPLOYMENT_SDK@
+MACOSX_DEPLOYMENT_VERSION = @MACOSX_DEPLOYMENT_VERSION@
+MACOSX_DEPLOYMENT_SDK = @MACOSX_DEPLOYMENT_SDK@
+
+ifneq "$(MACOSX_DEPLOYMENT_VERSION)" ""
+MACOSX_DEPLOYMENT_CC_OPTS = -mmacosx-version-min=$(MACOSX_DEPLOYMENT_VERSION) \
+ -isysroot $(MACOSX_DEPLOYMENT_SDK) \
+ --no-builtin-fprintf
+MACOSX_DEPLOYMENT_LD_OPTS = -mmacosx-version-min=$(MACOSX_DEPLOYMENT_VERSION) \
+ -Wl,-syslibroot,$(MACOSX_DEPLOYMENT_SDK)
+# We don't extend SRC_CC_OPTS and friends here directly, as (a) they may get
+# overwritten in build.mk and (b) we must not use the deployment options in
+# stage 1 or we get a linker error if the bootstrap compiler is for a more
+# recent OS version.
+#
+# We need --no-builtin-fprintf, as the use of the builtin function optimisation
+# for fprintf together with #include "PosixSource" in the RTS leads to the
+# use of fwrite$UNIX2003 (with GCC 4.0.1 on Mac OS X 10.5.2).
+endif