diff --git a/toolkit/crashreporter/jsoncpp/src/lib_json/moz.build b/toolkit/crashreporter/jsoncpp/src/lib_json/moz.build
index 2d51c2ce31..c5c2a29801 100644
--- a/toolkit/crashreporter/jsoncpp/src/lib_json/moz.build
+++ b/toolkit/crashreporter/jsoncpp/src/lib_json/moz.build
@@ -32,3 +32,8 @@ DISABLE_STL_WRAPPING = True
 Library('jsoncpp')
 
 include('/toolkit/crashreporter/crashreporter.mozbuild')
+
+if CONFIG['CLANG_CXX'] or CONFIG['CLANG_CL'] or CONFIG['GNU_CXX']:
+    CXXFLAGS += [
+        '-Wno-implicit-fallthrough',
+    ]