--- a/flutter/fml/BUILD.gn
+++ b/flutter/fml/BUILD.gn
@@ -291,6 +291,12 @@ source_set("string_conversion") {
   # conversion APIs.
   defines = [ "_LIBCPP_DISABLE_DEPRECATION_WARNINGS" ]
 
+  # libstdc++ diagnoses the same codecvt APIs via a compiler attribute rather
+  # than a compatibility macro.
+  if (!is_clang && !is_win) {
+    cflags_cc = [ "-Wno-deprecated-declarations" ]
+  }
+
   if (is_win) {
     sources += [
       "platform/win/wstring_conversion.cc",