diff --git a/src/core/kprotocolinfofactory.cpp b/src/core/kprotocolinfofactory.cpp
--- a/src/core/kprotocolinfofactory.cpp
+++ b/src/core/kprotocolinfofactory.cpp
@@ -71,10 +71,13 @@
 {
     QMutexLocker locker(&m_mutex);
 
+    // avoid filling the cache twice in succession
+    const bool wereAllProtocolsLoaded = m_allProtocolsLoaded;
+
     // fill cache, if not already done and use it
     fillCache();
     KProtocolInfoPrivate *info = m_cache.value(protocol);
-    if (!info) {
+    if (!info && wereAllProtocolsLoaded) {
         // Unknown protocol! Maybe it just got installed and our cache is out of date?
         qCDebug(KIO_CORE) << "Refilling KProtocolInfoFactory cache in the hope to find" << protocol;
         m_allProtocolsLoaded = false;