diff --git a/toolkit/content/widgets/videocontrols.css b/toolkit/content/widgets/videocontrols.css
index 75b5a8ab286b..d100682df41f 100644
--- a/toolkit/content/widgets/videocontrols.css
+++ b/toolkit/content/widgets/videocontrols.css
@@ -20,6 +20,7 @@
 .mediaControlsFrame {
   direction: ltr;
   /* Prevent unwanted style inheritance. See bug 554717. */
+  text-align: left;
   list-style-image: none !important;
   font: normal normal normal 100%/normal sans-serif !important;
   text-decoration: none !important;
diff --git a/toolkit/mozapps/extensions/AddonRepository.jsm b/toolkit/mozapps/extensions/AddonRepository.jsm
index c33eb2244b0a..11573851fcfc 100644
--- a/toolkit/mozapps/extensions/AddonRepository.jsm
+++ b/toolkit/mozapps/extensions/AddonRepository.jsm
@@ -1257,8 +1257,10 @@ var AddonRepository = {
   // Parses addon_compatibility nodes, that describe compatibility overrides.
   _parseAddonCompatElement: function(aResultObj, aElement) {
     let guid = this._getDescendantTextContent(aElement, "guid");
-    if (!guid)
+    if (!guid) {
+        LOG("Compatibility override is missing guid.");
       return;
+    }
 
     let compat = {id: guid};
     compat.hosted = aElement.getAttribute("hosted") != "false";
@@ -1292,21 +1294,31 @@ var AddonRepository = {
     function parseRangeNode(aNode) {
       let type = aNode.getAttribute("type");
       // Only "incompatible" (blacklisting) is supported for now.
-      if (type != "incompatible")
+      if (type != "incompatible") {
+        LOG("Compatibility override of unsupported type found.");
         return null;
+      }
 
       let override = new AddonManagerPrivate.AddonCompatibilityOverride(type);
 
       override.minVersion = this._getDirectDescendantTextContent(aNode, "min_version");
       override.maxVersion = this._getDirectDescendantTextContent(aNode, "max_version");
 
-      if (!override.minVersion || !override.maxVersion)
+      if (!override.minVersion) {
+        LOG("Compatibility override is missing min_version.");
         return null;
+      }
+      if (!override.maxVersion) {
+        LOG("Compatibility override is missing max_version.");
+        return null;
+      }
 
       let appRanges = aNode.querySelectorAll("compatible_applications > application");
       let appRange = findMatchingAppRange.bind(this)(appRanges);
-      if (!appRange)
+      if (!appRange) {
+        LOG("Compatibility override is missing a valid application range.");
         return null;
+      }
 
       override.appID = appRange.appID;
       override.appMinVersion = appRange.appMinVersion;
diff --git a/toolkit/mozapps/extensions/XPIProvider.jsm b/toolkit/mozapps/extensions/XPIProvider.jsm
index 0288121449d1..530add649a09 100644
--- a/toolkit/mozapps/extensions/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/XPIProvider.jsm
@@ -6148,6 +6148,7 @@ AddonInstall.prototype = {
         if (aRepoAddon) {
           aAddon._repositoryAddon = aRepoAddon;
           aAddon.compatibilityOverrides = aRepoAddon.compatibilityOverrides;
+          aAddon.appDisabled = !isUsableAddon(aAddon);
           aCallback();
           return;
         }
@@ -6159,6 +6160,7 @@ AddonInstall.prototype = {
             aAddon.compatibilityOverrides = aRepoAddon ?
                                               aRepoAddon.compatibilityOverrides :
                                               null;
+            aAddon.appDisabled = !isUsableAddon(aAddon);
             aCallback();
           });
         });
diff --git a/toolkit/mozapps/extensions/test/addons/test_install6/install.rdf b/toolkit/mozapps/extensions/test/addons/test_install6/install.rdf
new file mode 100644
index 000000000000..b1f97c1fd47a
--- /dev/null
+++ b/toolkit/mozapps/extensions/test/addons/test_install6/install.rdf
@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+
+<!-- An extension that has a compatibility override making it incompatible. -->
+<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+     xmlns:em="http://www.mozilla.org/2004/em-rdf#">
+
+  <Description about="urn:mozilla:install-manifest">
+    <em:id>addon6@tests.mozilla.org</em:id>
+    <em:version>1.0</em:version>
+
+    <!-- Front End MetaData -->
+    <em:name>Addon Test 6</em:name>
+    <em:description>Test Description</em:description>
+
+    <em:targetApplication>
+      <Description>
+        <em:id>xpcshell@tests.mozilla.org</em:id>
+        <em:minVersion>1</em:minVersion>
+        <em:maxVersion>1</em:maxVersion>
+      </Description>
+    </em:targetApplication>
+
+  </Description>
+</RDF>
diff --git a/toolkit/mozapps/extensions/test/xpcshell/data/test_install.xml b/toolkit/mozapps/extensions/test/xpcshell/data/test_install.xml
index 7c47f8a42bf4..33f14a2fdcff 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/data/test_install.xml
+++ b/toolkit/mozapps/extensions/test/xpcshell/data/test_install.xml
@@ -31,4 +31,23 @@
     <compatible_os>ALL</compatible_os>
     <install size="2">http://example.com/browser/toolkit/mozapps/extensions/test/browser/addons/browser_install1_2.xpi</install>
   </addon>
+
+  <addon_compatibility hosted="false">
+    <guid>addon6@tests.mozilla.org</guid>
+    <name>Addon Test 6</name>
+    <version_ranges>
+      <version_range type="incompatible">
+        <min_version>1.0</min_version>
+        <max_version>1.0</max_version>
+        <compatible_applications>
+          <application>
+            <name>XPCShell</name>
+            <min_version>1.0</min_version>
+            <max_version>1.0</max_version>
+            <appID>xpcshell@tests.mozilla.org</appID>
+          </application>
+        </compatible_applications>
+      </version_range>
+    </version_ranges>
+  </addon_compatibility>
 </searchresults>
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_install.js b/toolkit/mozapps/extensions/test/xpcshell/test_install.js
index 21283692f8f4..bcc153a673a0 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_install.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_install.js
@@ -1678,7 +1678,52 @@ function check_test_28(install) {
 function finish_test_28(install) {
   prepare_test({}, [
     "onDownloadCancelled"
-  ], do_test_finished);
+  ], run_test_29);
 
   install.cancel();
 }
+
+// Tests that an install with a matching compatibility override has appDisabled
+// set correctly.
+function run_test_29() {
+  Services.prefs.setBoolPref("extensions.getAddons.cache.enabled", true);
+
+  prepare_test({ }, [
+    "onNewInstall"
+  ]);
+
+  let url = "http://localhost:4444/addons/test_install6.xpi";
+  AddonManager.getInstallForURL(url, function(install) {
+    ensure_test_completed();
+
+    do_check_neq(install, null);
+    do_check_eq(install.version, "1.0");
+    do_check_eq(install.name, "Addon Test 6");
+    do_check_eq(install.state, AddonManager.STATE_AVAILABLE);
+
+    AddonManager.getInstallsByTypes(null, function(activeInstalls) {
+      do_check_eq(activeInstalls.length, 1);
+      do_check_eq(activeInstalls[0], install);
+
+      prepare_test({}, [
+        "onDownloadStarted",
+        "onDownloadEnded"
+      ], check_test_29);
+      install.install();
+    });
+  }, "application/x-xpinstall", null, "Addon Test 6", null, "1.0");
+}
+
+function check_test_29(install) {
+  //ensure_test_completed();
+  do_check_eq(install.state, AddonManager.STATE_DOWNLOADED);
+  do_check_neq(install.addon, null);
+  do_check_false(install.addon.isCompatible);
+  do_check_true(install.addon.appDisabled);
+
+  prepare_test({}, [
+    "onDownloadCancelled"
+  ], do_test_finished);
+  install.cancel();
+  return false;
+}