diff --git a/src/libs/qmljs/persistenttrie.cpp b/src/libs/qmljs/persistenttrie.cpp
index 1d6c9bf5ba5..6cd1b726b27 100644
--- a/src/libs/qmljs/persistenttrie.cpp
+++ b/src/libs/qmljs/persistenttrie.cpp
@@ -526,14 +526,14 @@ QDebug &TrieNode::describe(QDebug &dbg, const TrieNode::Ptr &trie,
     return dbg;
 }
 
-QDebug &operator<<(QDebug &dbg, const TrieNode::Ptr &trie)
+QDebug operator<<(QDebug dbg, const TrieNode::Ptr &trie)
 {
     dbg.nospace()<<"Trie{\n";
     TrieNode::describe(dbg,trie,0);
     dbg << "}";
     return dbg.space();
 }
-QDebug &operator<<(QDebug &dbg, const Trie &trie)
+QDebug operator<<(QDebug dbg, const Trie &trie)
 {
     dbg.nospace()<<"Trie{\n";
     TrieNode::describe(dbg,trie.trie,0);
diff --git a/src/libs/qmljs/persistenttrie.h b/src/libs/qmljs/persistenttrie.h
index 19d7c3a0e79..bb970622d54 100644
--- a/src/libs/qmljs/persistenttrie.h
+++ b/src/libs/qmljs/persistenttrie.h
@@ -98,8 +98,8 @@ public:
     bool operator==(const Trie &o);
     bool operator!=(const Trie &o);
 
-    friend QMLJS_EXPORT QDebug &operator<<(QDebug &dbg, const TrieNode::Ptr &trie);
-    friend QMLJS_EXPORT QDebug &operator<<(QDebug &dbg, const Trie &trie);
+    friend QMLJS_EXPORT QDebug operator<<(QDebug dbg, const TrieNode::Ptr &trie);
+    friend QMLJS_EXPORT QDebug operator<<(QDebug dbg, const Trie &trie);
 
     TrieNode::Ptr trie;
 };
@@ -120,8 +120,8 @@ template <typename T> void enumerateTrieNode(const TrieNode::Ptr &trie, T &t,
 QMLJS_EXPORT int matchStrength(const QString &searchStr, const QString &str);
 QMLJS_EXPORT QStringList matchStrengthSort(const QString &searchString, QStringList &res);
 
-QMLJS_EXPORT QDebug &operator<<(QDebug &dbg, const TrieNode::Ptr &trie);
-QMLJS_EXPORT QDebug &operator<<(QDebug &dbg, const Trie &trie);
+QMLJS_EXPORT QDebug operator<<(QDebug dbg, const TrieNode::Ptr &trie);
+QMLJS_EXPORT QDebug operator<<(QDebug dbg, const Trie &trie);
 
 } // end namespace PersistentTrie
 } // end namespace QmlJS