diff --git a/core/language/en-GB/Import.multids b/core/language/en-GB/Import.multids
index 083086606..3c7ced320 100644
--- a/core/language/en-GB/Import.multids
+++ b/core/language/en-GB/Import.multids
@@ -19,3 +19,4 @@ Upgrader/Plugins/Upgraded: Upgraded plugin from <<incoming>> to <<upgraded>>
 Upgrader/State/Suppressed: Blocked temporary state tiddler
 Upgrader/System/Suppressed: Blocked system tiddler
 Upgrader/ThemeTweaks/Created: Migrated theme tweak from <$text text=<<from>>/>
+Warning/Core: You are about importing risky tiddlers (<<titles>>). It is strongly recommend in the strongest terms NOT to use any hack that requires overwriting a core module, because it is likely to make the system unusable. Never import such tiddlers into an important wiki, just into a testing environment!
diff --git a/core/modules/widgets/navigator.js b/core/modules/widgets/navigator.js
index 2bf0ac594..3109fdea9 100755
--- a/core/modules/widgets/navigator.js
+++ b/core/modules/widgets/navigator.js
@@ -485,7 +485,8 @@ NavigatorWidget.prototype.handleNewTiddlerEvent = function(event) {
 // Import JSON tiddlers into a pending import tiddler
 NavigatorWidget.prototype.handleImportTiddlersEvent = function(event) {
 	// Get the tiddlers
-	var tiddlers = [];
+	var tiddlers = [],
+		warning = [];
 	try {
 		tiddlers = JSON.parse(event.param);
 	} catch(e) {
@@ -506,10 +507,26 @@ NavigatorWidget.prototype.handleImportTiddlersEvent = function(event) {
 		tiddlerFields.title = $tw.utils.trim(tiddlerFields.title);
 		var title = tiddlerFields.title;
 		if(title) {
+			if(title.indexOf('$:/core/') === 0) {
+				warning.push(title);
+			}
 			incomingTiddlers.push(title);
 			importData.tiddlers[title] = tiddlerFields;
 		}
 	});
+	// Show warning about risky tiddlers
+	if(warning.length) {
+		var titles = [];
+		$tw.utils.each(warning,function(title) {
+			titles.push(title);
+		});
+		var logger = new $tw.utils.Logger("import");
+		logger.alert($tw.language.getString(
+			"Import/Warning/Core",
+			{variables: {
+			"titles": titles.join(", "),
+		}}));
+	}
 	// Give the active upgrader modules a chance to process the incoming tiddlers
 	var messages = this.wiki.invokeUpgraders(incomingTiddlers,importData.tiddlers);
 	$tw.utils.each(messages,function(message,title) {