diff --git a/mkpkg b/mkpkg
index c1ea8ed3c..7a4e8b844 100755
--- a/mkpkg
+++ b/mkpkg
@@ -229,7 +229,10 @@ case "$osversion" in
     macos*)
 	# Build universal binaries (intel-only) targetting Mac OS X 10.5
 	ARCH_FLAGS="-arch i386 -arch x86_64"
-	SDK_FLAGS="-isysroot /Developer/SDKs/MacOSX10.5.sdk -mmacosx-version-min=10.5"
+	if test "${osversion}" != "`$top_srcdir/pp --probe`"; then
+	    sdkvers=`echo "${osversion}" | sed 's/^macos\([0-9][0-9]\)\([0-9]*\)-.*$/\1.\2/'`
+	    SDK_FLAGS="-isysroot /Developer/SDKs/MacOSX${sdkvers}.sdk -mmacosx-version-min=${sdkvers}"
+	fi
 	export CFLAGS="-O2 -g $ARCH_FLAGS $SDK_FLAGS"
 	export LDFLAGS="$ARCH_FLAGS $SDK_FLAGS"
 	# Note, must indent with tabs, not spaces due to IFS trickery