diff --git a/src/libs/qmljs/persistenttrie.cpp b/src/libs/qmljs/persistenttrie.cpp
index d41c5d2443e..6c604882490 100644
--- a/src/libs/qmljs/persistenttrie.cpp
+++ b/src/libs/qmljs/persistenttrie.cpp
@@ -583,12 +583,12 @@ bool Trie::isEmpty() const
     return trie.isNull(); // assuming to never generate an empty non null trie
 }
 
-bool Trie::operator==(const Trie &o)
+bool Trie::operator==(const Trie &o) const
 {
     return TrieNode::isSame(trie,o.trie);
 }
 
-bool Trie::operator!=(const Trie &o)
+bool Trie::operator!=(const Trie &o) const
 {
     return !TrieNode::isSame(trie,o.trie);
 }
diff --git a/src/libs/qmljs/persistenttrie.h b/src/libs/qmljs/persistenttrie.h
index f9457723c4b..f0e52a2662b 100644
--- a/src/libs/qmljs/persistenttrie.h
+++ b/src/libs/qmljs/persistenttrie.h
@@ -73,8 +73,8 @@ public:
     void replace(const QHash<QString, QString> &replacements);
 
     bool isEmpty() const;
-    bool operator==(const Trie &o);
-    bool operator!=(const Trie &o);
+    bool operator==(const Trie &o) const;
+    bool operator!=(const Trie &o) const;
 
     friend QMLJS_EXPORT QDebug operator<<(QDebug dbg, const TrieNode::Ptr &trie);
     friend QMLJS_EXPORT QDebug operator<<(QDebug dbg, const Trie &trie);