diff --git a/devel/boehmgc/Portfile b/devel/boehmgc/Portfile
index 3041965557b5..8e1253a26294 100644
--- a/devel/boehmgc/Portfile
+++ b/devel/boehmgc/Portfile
@@ -25,6 +25,10 @@ long_description \
 github.tarball_from releases
 distname            gc-${version}
 
+# gc_atomic_ops.h: warning: implicit declaration of function '__atomic_compare_exchange_n'
+# gc_atomic_ops.h: error: '__ATOMIC_RELAXED' undeclared (first use in this function)
+compiler.c_standard 2011
+
 configure.args  --enable-cplusplus \
                 --enable-static \
                 --with-libatomic-ops=none