diff --git a/src/core/kprotocolinfofactory.cpp b/src/core/kprotocolinfofactory.cpp
--- a/src/core/kprotocolinfofactory.cpp
+++ b/src/core/kprotocolinfofactory.cpp
@@ -37,16 +37,16 @@
 }
 
 KProtocolInfoFactory::KProtocolInfoFactory()
-    : m_allProtocolsLoaded(false)
+    : m_cacheDirty(true)
 {
 }
 
 KProtocolInfoFactory::~KProtocolInfoFactory()
 {
     QMutexLocker locker(&m_mutex);
     qDeleteAll(m_cache);
     m_cache.clear();
-    m_allProtocolsLoaded = false;
+    m_cacheDirty = true;
 }
 
 QStringList KProtocolInfoFactory::protocols()
@@ -71,31 +71,32 @@
 {
     QMutexLocker locker(&m_mutex);
 
-    // fill cache, if not already done and use it
-    fillCache();
+    const bool filled = fillCache();
+
     KProtocolInfoPrivate *info = m_cache.value(protocol);
-    if (!info) {
+    if (!info && !filled) {
         // 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 Maybe it just got installed and our cache is out of date?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;
-        qDeleteAll(m_cache);
-        m_cache.clear();
+        m_cacheDirty = true;
         fillCache();
         info = m_cache.value(protocol);
     }
     return info;
 }
 
-void KProtocolInfoFactory::fillCache()
+bool KProtocolInfoFactory::fillCache()
 {
     // mutex MUST be locked from the outside!
     Q_ASSERT(!m_mutex.tryLock());
 
     // no work if filled
-    if (m_allProtocolsLoaded) {
-        return;
+    if (!m_cacheDirty) {
+        return false;
     }
 
+    qDeleteAll(m_cache);
+    m_cache.clear();
+
     // first: search for meta data protocol info, that might be bundled with applications
     // we search in all library paths inside kf5/kio
     Q_FOREACH (const KPluginMetaData &md, KPluginLoader::findPlugins("kf5/kio")) {
@@ -134,5 +135,6 @@
     }
 
     // all done, don't do it again
-    m_allProtocolsLoaded = true;
+    m_cacheDirty = false;
+    return true;
 }
diff --git a/src/core/kprotocolinfofactory_p.h b/src/core/kprotocolinfofactory_p.h
--- a/src/core/kprotocolinfofactory_p.h
+++ b/src/core/kprotocolinfofactory_p.h
@@ -69,11 +69,11 @@
     /**
      * Fill the internal cache.
      */
-    void fillCache();
+    bool fillCache();
 
     typedef QHash<QString, KProtocolInfoPrivate *> ProtocolCache;
     ProtocolCache m_cache;
-    bool m_allProtocolsLoaded;
+    bool m_cacheDirty;
     mutable QMutex m_mutex; // protects m_cache and m_allProtocolsLoaded
 };