diff --git a/src/js/cosmetic-filtering.js b/src/js/cosmetic-filtering.js
index 177dad499..e2a8f704a 100644
--- a/src/js/cosmetic-filtering.js
+++ b/src/js/cosmetic-filtering.js
@@ -1039,6 +1039,7 @@ FilterContainer.prototype.pruneSelectorCacheAsync = function() {
         // console.debug('pruneSelectorCacheAsync: flushing "%s"', hostname);
         entry.dispose();
         delete cache[hostname];
+        this.selectorCacheCount -= 1;
     }
     this.triggerSelectorCachePruner();
 };