diff --git a/src/node.cc b/src/node.cc
index fb85af7227..ce49a5c431 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -4191,6 +4191,14 @@ void Init(int* argc,
                             DispatchDebugMessagesAsyncCallback));
   uv_unref(reinterpret_cast<uv_handle_t*>(&dispatch_debug_messages_async));
 
+#if defined(NODE_HAVE_I18N_SUPPORT)
+  // Set the ICU casing flag early
+  // so the user can disable a flag --foo at run-time by passing
+  // --no_foo from the command line.
+  const char icu_case_mapping[] = "--icu_case_mapping";
+  V8::SetFlagsFromString(icu_case_mapping, sizeof(icu_case_mapping) - 1);
+#endif
+
 #if defined(NODE_V8_OPTIONS)
   // Should come before the call to V8::SetFlagsFromCommandLine()
   // so the user can disable a flag --foo at run-time by passing
diff --git a/test/parallel/test-intl.js b/test/parallel/test-intl.js
index 938099f2e3..1058650830 100644
--- a/test/parallel/test-intl.js
+++ b/test/parallel/test-intl.js
@@ -50,6 +50,11 @@ if (!common.hasIntl) {
     return;
   }
 
+  // Check casing
+  {
+    assert.strictEqual('I'.toLocaleLowerCase('tr'), 'ı');
+  }
+
   // Check with toLocaleString
   {
     const localeString = dtf.format(date0);