diff --git a/toolkit/components/extensions/Extension.jsm b/toolkit/components/extensions/Extension.jsm
index 84c870faaf8a..ddab409cce08 100644
--- a/toolkit/components/extensions/Extension.jsm
+++ b/toolkit/components/extensions/Extension.jsm
@@ -1164,7 +1164,13 @@ Extension.prototype = extend(Object.create(ExtensionData.prototype), {
     }
     this.whiteListedHosts = new MatchPattern(whitelist);
 
-    this.webAccessibleResources = new MatchGlobs(manifest.web_accessible_resources || []);
+    // Strip leading slashes from web_accessible_resources.
+    let strippedWebAccessibleResources = [];
+    if (manifest.web_accessible_resources) {
+      strippedWebAccessibleResources = manifest.web_accessible_resources.map(path => path.replace(/^\/+/, ""));
+    }
+
+    this.webAccessibleResources = new MatchGlobs(strippedWebAccessibleResources);
 
     for (let directive in manifest) {
       if (manifest[directive] !== null) {
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html b/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html
index cf46886a3077..8d83dbd0ca08 100644
--- a/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html
+++ b/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html
@@ -96,7 +96,7 @@ add_task(function* test_web_accessible_resources() {
       ],
 
       "web_accessible_resources": [
-        "accessible.html",
+        "/accessible.html",
         "wild*.html",
       ],
     },