Index: lib/filterComposer.js
diff --git a/lib/filterComposer.js b/lib/filterComposer.js
index fe5dcdf3071e1762e31cfb4e4bd461a67bbcac23..361c4b30a4c9e10ead1990d93481d56ef112a5d5 100644
--- a/lib/filterComposer.js
+++ b/lib/filterComposer.js
@@ -188,6 +188,12 @@ port.on("composer.openDialog", (message, sender) =>
         // we must check the response too.
         if (!response)
           throw new Error();
+
+        // Sometimes Firefox doesn't draw the window's contents initially, so we
+        // resize the window slightly as a workaround.
+        // https://issues.adblockplus.org/ticket/6493
+        if (info.application == "firefox")
+          browser.windows.update(window.id, {width: window.width + 2});
       }).catch(e =>
       {
         // Firefox sometimes sets the status for a window to "complete" before