--- a/freebsd-lib-9.1.ebuild	
+++ a/freebsd-lib-9.1.ebuild	
@@ -169,6 +169,7 @@ src_prepare() {
 		# shouldn't be a symlink to /usr/src/sys (which should be already patched)
 		epatch "${FILESDIR}"/${PN}-7.1-types.h-fix.patch
 		epatch "${FILESDIR}"/freebsd-sources-9.0-sysctluint.patch
+		epatch "${FILESDIR}"/freebsd-sources-9.1-cdefs.h-gcc47.patch
 		return 0
 	fi