diff --git a/dev-libs/crypto++/crypto++-5.6.4-r2.ebuild b/dev-libs/crypto++/crypto++-5.6.4-r2.ebuild
index b21a0040628f9..81b727a5f9116 100644
--- a/dev-libs/crypto++/crypto++-5.6.4-r2.ebuild
+++ b/dev-libs/crypto++/crypto++-5.6.4-r2.ebuild
@@ -38,7 +38,7 @@ src_compile() {
 	# higher optimizations cause problems
 	replace-flags -O3 -O2
 	# ASM isn't Darwin/Mach-O ready, #479554, buildsys doesn't grok CPPFLAGS
-	[[ ${CHOST} == *-darwin* ]] && append-flags -DCRYPTOPP_DISABLE_X86ASM
+	[[ ${CHOST} == *-darwin* ]] && append-cxxflags -DCRYPTOPP_DISABLE_ASM
 
 	emake -f GNUmakefile all shared
 }