diff --git a/toolkit/components/extensions/ExtensionStorage.jsm b/toolkit/components/extensions/ExtensionStorage.jsm
index 02e496a56ad5..c09e58965409 100644
--- a/toolkit/components/extensions/ExtensionStorage.jsm
+++ b/toolkit/components/extensions/ExtensionStorage.jsm
@@ -81,12 +81,7 @@ this.ExtensionStorage = {
         extData[prop] = items[prop];
       }
 
-      let listeners = this.listeners.get(extensionId);
-      if (listeners) {
-        for (let listener of listeners) {
-          listener(changes);
-        }
-      }
+      this.notifyListeners(extensionId, changes);
 
       return this.write(extensionId);
     });
@@ -106,13 +101,24 @@ this.ExtensionStorage = {
         delete extData[prop];
       }
 
-      let listeners = this.listeners.get(extensionId);
-      if (listeners) {
-        for (let listener of listeners) {
-          listener(changes);
+      this.notifyListeners(extensionId, changes);
+
+      return this.write(extensionId);
+    });
+  },
+
+  clear(extensionId) {
+    return this.read(extensionId).then(extData => {
+      let changes = {};
+      if (extData) {
+        for (let prop of Object.keys(extData)) {
+          changes[prop] = {oldValue: extData[prop]};
+          delete extData[prop];
         }
       }
 
+      this.notifyListeners(extensionId, changes);
+
       return this.write(extensionId);
     });
   },
@@ -158,6 +164,15 @@ this.ExtensionStorage = {
     listeners.delete(listener);
   },
 
+  notifyListeners(extensionId, changes) {
+    let listeners = this.listeners.get(extensionId);
+    if (listeners) {
+      for (let listener of listeners) {
+        listener(changes);
+      }
+    }
+  },
+
   init() {
     Services.obs.addObserver(this, "extension-invalidate-storage-cache", false);
     Services.obs.addObserver(this, "xpcom-shutdown", false);
diff --git a/toolkit/components/extensions/ext-storage.js b/toolkit/components/extensions/ext-storage.js
index ae59b87f50ed..ed91dbd88fff 100644
--- a/toolkit/components/extensions/ext-storage.js
+++ b/toolkit/components/extensions/ext-storage.js
@@ -33,6 +33,13 @@ extensions.registerPrivilegedAPI("storage", (extension, context) => {
             }
           });
         },
+        clear: function(callback) {
+          ExtensionStorage.clear(extension.id).then(() => {
+            if (callback) {
+              runSafe(context, callback);
+            }
+          });
+        },
       },
 
       onChanged: new EventManager(context, "storage.local.onChanged", fire => {
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_storage.html b/toolkit/components/extensions/test/mochitest/test_ext_storage.html
index 180758489777..4b982da7442a 100644
--- a/toolkit/components/extensions/test/mochitest/test_ext_storage.html
+++ b/toolkit/components/extensions/test/mochitest/test_ext_storage.html
@@ -31,6 +31,12 @@ function backgroundScript() {
     });
   }
 
+  function clear(items) {
+    return new Promise(resolve => {
+      browser.storage.local.clear(resolve);
+    });
+  }
+
   function check(prop, value) {
     return get(null).then(data => {
       browser.test.assertEq(data[prop], value, "null getter worked for " + prop);
@@ -110,6 +116,18 @@ function backgroundScript() {
     browser.test.assertFalse("test-prop1" in data, "prop1 absent");
     browser.test.assertFalse("test-prop2" in data, "prop2 absent");
 
+  // test storage.clear
+  }).then(() => {
+    return set({"test-prop1": "value1", "test-prop2": "value2"});
+  }).then(() => {
+    return clear();
+  }).then(() => {
+    checkChanges({"test-prop1": {oldValue: "value1"}, "test-prop2": {oldValue: "value2"}});
+    return get(["test-prop1", "test-prop2"]);
+  }).then(data => {
+    browser.test.assertFalse("test-prop1" in data, "prop1 absent");
+    browser.test.assertFalse("test-prop2" in data, "prop2 absent");
+
   // Test cache invalidation.
   }).then(() => {
     return set({"test-prop1": "value1", "test-prop2": "value2"});