diff --git a/content/treestyletab/res/tabFx2Compatible.css b/content/treestyletab/res/tabFx2Compatible.css
index 90e687bb..5e38cc99 100644
--- a/content/treestyletab/res/tabFx2Compatible.css
+++ b/content/treestyletab/res/tabFx2Compatible.css
@@ -14,33 +14,75 @@
 
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
-:root[tabFx2Compatible="5"]
+:root[tabFx2Compatible="6"]
   .tabbrowser-tab {
 	-moz-binding: url(tabFx2Compatible.xml#tabbrowser-tab) !important;
 }
 
-:root[tabFx2Compatible="5"]:not([tabFx2Compatible-flags~="png-throbber"])
+:root[tabFx2Compatible="6"]:not([tabFx2Compatible-flags~="png-throbber"])
   .tabbrowser-tab[busy] > hbox > stack > .tab-icon-image {
 	list-style-image: url("chrome://global/skin/throbber/Throbber-small.gif") !important;
 	opacity: 0.6;
 }
 
-:root[tabFx2Compatible="5"][tabFx2Compatible-flags~="png-throbber"]
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="png-throbber"]
   .tabbrowser-tab[busy] > hbox > stack > .tab-icon-image {
 	list-style-image: url("chrome://global/skin/icons/loading_16.png") !important;
 }
 
-:root[tabFx2Compatible="5"][tabFx2Compatible-flags~="mac"][tabFx2Compatible-flags~="png-throbber"]
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="mac"][tabFx2Compatible-flags~="png-throbber"]
   .tabbrowser-tab .tab-icon-image {
 	list-style-image: url("chrome://global/skin/tree/item.png");
 }
 
-:root[tabFx2Compatible="5"][tabFx2Compatible-flags~="mac"]
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="mac"]
   .tabbrowser-tab:not(:hover):not([selected="true"]) .tab-icon-image {
 	opacity: 0.6;
 }
 
-:root[tabFx2Compatible="5"]
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy] > hbox > stack > .tab-icon-image {
+	list-style-image: url("chrome://browser/skin/tabbrowser/progress.png") !important;
+	-moz-image-region: rect(0, 16px, 16px, 0);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][stalled] > hbox > stack > .tab-icon-image {
+	list-style-image: url("chrome://browser/skin/tabbrowser/progress-pulsing.png") !important;
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="1"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 32px, 16px, 16px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="2"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 48px, 16px, 32px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="3"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 64px, 16px, 48px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="4"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 80px, 16px, 64px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="5"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 96px, 16px, 80px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="6"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 112px, 16px, 96px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="7"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 128px, 16px, 112px);
+}
+:root[tabFx2Compatible="6"][tabFx2Compatible-flags~="pie"]
+  .tabbrowser-tab[busy][progress="8"] > hbox > stack > .tab-icon-image {
+	-moz-image-region: rect(0, 144px, 16px, 128px);
+}
+
+:root[tabFx2Compatible="6"]
   .tabbrowser-tab[selected="true"]:focus > hbox > .tab-text {
 	border: 1px dotted -moz-DialogText;
 }
diff --git a/content/treestyletab/res/tabFx2Compatible.xul b/content/treestyletab/res/tabFx2Compatible.xul
index 02ca3353..3d370441 100644
--- a/content/treestyletab/res/tabFx2Compatible.xul
+++ b/content/treestyletab/res/tabFx2Compatible.xul
@@ -19,7 +19,7 @@
 window.addEventListener('DOMContentLoaded', function() {
 	window.removeEventListener('DOMContentLoaded', arguments.callee, true);
 
-	const currentRevision = 5;
+	const currentRevision = 6;
 
 	var b = document.getElementById('content');
 	if (!b || b.localName != 'tabbrowser') return;
@@ -68,6 +68,8 @@ window.addEventListener('DOMContentLoaded', function() {
 				flags.push('mac');
 			if ('nsPIPlacesDatabase' in Components.interfaces)
 				flags.push('png-throbber');
+			if (b.mTabProgressListener.toSource().indexOf('_startStalledTimer') > -1)
+				flags.push('pie');
 			root.setAttribute('tabFx2Compatible-flags', flags.join(' '));
 			break;
 	}