diff --git a/platform/chromium/vapi-common.js b/platform/chromium/vapi-common.js
index 56b192e..1763e5e 100644
--- a/platform/chromium/vapi-common.js
+++ b/platform/chromium/vapi-common.js
@@ -81,6 +81,10 @@ vAPI.closePopup = function() {
     window.open('','_self').close();
 };
 
+vAPI.resizePopup = function() {
+    // Nothing to do: chromium API takes care to resize the popup
+};
+
 /******************************************************************************/
 
 // A localStorage-like object which should be accessible from the
diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index d1b74fd..a0aa4ca 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -2022,6 +2022,15 @@ vAPI.toolbarButton = {
             }
         };
 
+        var onResizeRequested = function() {
+            var body = iframe.contentDocument.body;
+            if ( body.getAttribute('data-resize-popup') !== 'true' ) {
+                return;
+            }
+            body.removeAttribute('data-resize-popup');
+            resizePopupDelayed();
+        };
+
         var onPopupReady = function() {
             var win = this.contentWindow;
 
@@ -2033,16 +2042,14 @@ vAPI.toolbarButton = {
                 tbb.onBeforePopupReady.call(this);
             }
 
-            new win.MutationObserver(resizePopupDelayed).observe(win.document.body, {
+            var mutationObserver = new win.MutationObserver(onResizeRequested);
+            mutationObserver.observe(win.document.body, {
                 attributes: true,
-                characterData: true,
-                subtree: true
+                attributeFilter: [ 'data-resize-popup' ]
             });
-
-            resizePopupDelayed();
         };
 
-        iframe.addEventListener('load', onPopupReady, true);
+        iframe.addEventListener('DOMContentLoaded', onPopupReady, true);
     };
 })();
 
diff --git a/platform/firefox/vapi-common.js b/platform/firefox/vapi-common.js
index 89e4423..c8910e0 100644
--- a/platform/firefox/vapi-common.js
+++ b/platform/firefox/vapi-common.js
@@ -120,6 +120,10 @@ vAPI.closePopup = function() {
     sendAsyncMessage(location.host + ':closePopup');
 };
 
+vAPI.resizePopup = function() {
+    document.body.setAttribute('data-resize-popup', 'true');
+};
+
 /******************************************************************************/
 
 // A localStorage-like object which should be accessible from the
diff --git a/src/js/popup.js b/src/js/popup.js
index b480bfc..9b1f002 100644
--- a/src/js/popup.js
+++ b/src/js/popup.js
@@ -288,6 +288,7 @@ function toggleCollapseState(elem) {
     } else {
         toggleSpecificCollapseState(elem);
     }
+    vAPI.resizePopup();
 }
 
 function toggleMainCollapseState(uelem) {
@@ -368,6 +369,7 @@ function updateMatrixColors() {
         cell = cells.nodeAt(i);
         cell.className = 'matCell ' + getCellClass(cell.hostname, cell.reqType);
     }
+    vAPI.resizePopup();
 }
 
 /******************************************************************************/
@@ -393,6 +395,7 @@ function updateMatrixBehavior() {
         }
         section.toggleClass('collapsible', subdomainRows.filter('.collapsible').length > 0);
     }
+    vAPI.resizePopup();
 }
 
 /******************************************************************************/
@@ -475,6 +478,7 @@ var endMatrixUpdate = function() {
     updateMatrixBehavior();
     matrixList.css('display', '');
     matrixList.appendTo('.paneContent');
+    vAPI.resizePopup();
 };
 
 var createMatrixGroup = function() {
@@ -1363,6 +1367,7 @@ uDom('#matList').on('click', '.g4Meta', function() {
         .toggleClass('g4Collapsed')
         .hasClass('g4Collapsed');
     setUISetting('popupHideBlacklisted', collapsed);
+    vAPI.resizePopup();
 });
 
 /******************************************************************************/