diff --git a/src/plugins/cppeditor/semantichighlighter.cpp b/src/plugins/cppeditor/semantichighlighter.cpp
index 473991787d0..c04b9270aa9 100644
--- a/src/plugins/cppeditor/semantichighlighter.cpp
+++ b/src/plugins/cppeditor/semantichighlighter.cpp
@@ -63,15 +63,20 @@ void SemanticHighlighter::run()
     connectWatcher();
 
     m_revision = documentRevision();
+    m_seenBlocks.clear();
     qCDebug(log) << "starting runner for document revision" << m_revision;
     m_watcher->setFuture(m_highlightingRunner());
 }
 
-static Parentheses getClearedParentheses(const QTextBlock &block)
+Parentheses SemanticHighlighter::getClearedParentheses(const QTextBlock &block)
 {
-    return Utils::filtered(TextDocumentLayout::parentheses(block), [](const Parenthesis &p) {
-        return p.source != parenSource();
-    });
+    Parentheses parens = TextDocumentLayout::parentheses(block);
+    if (m_seenBlocks.insert(block.blockNumber()).second) {
+        parens = Utils::filtered(parens, [](const Parenthesis &p) {
+            return p.source != parenSource();
+        });
+    }
+    return parens;
 }
 
 void SemanticHighlighter::onHighlighterResultAvailable(int from, int to)
diff --git a/src/plugins/cppeditor/semantichighlighter.h b/src/plugins/cppeditor/semantichighlighter.h
index b34c49ce87a..fb1a704e6c3 100644
--- a/src/plugins/cppeditor/semantichighlighter.h
+++ b/src/plugins/cppeditor/semantichighlighter.h
@@ -8,14 +8,21 @@
 #include <QFutureWatcher>
 #include <QScopedPointer>
 #include <QTextCharFormat>
+#include <QVector>
 
 #include <functional>
+#include <set>
 
 namespace TextEditor {
 class HighlightingResult;
+class Parenthesis;
 class TextDocument;
 }
 
+QT_BEGIN_NAMESPACE
+class QTextBlock;
+QT_END_NAMESPACE
+
 namespace CppEditor {
 
 class CPPEDITOR_EXPORT SemanticHighlighter : public QObject
@@ -66,6 +73,7 @@ private:
     void disconnectWatcher();
 
     unsigned documentRevision() const;
+    QVector<TextEditor::Parenthesis> getClearedParentheses(const QTextBlock &block);
 
 private:
     TextEditor::TextDocument *m_baseTextDocument;
@@ -73,6 +81,7 @@ private:
     unsigned m_revision = 0;
     QScopedPointer<QFutureWatcher<TextEditor::HighlightingResult>> m_watcher;
     QHash<int, QTextCharFormat> m_formatMap;
+    std::set<int> m_seenBlocks;
 
     HighlightingRunner m_highlightingRunner;
 };
diff --git a/src/plugins/texteditor/textdocumentlayout.h b/src/plugins/texteditor/textdocumentlayout.h
index d6f847e4810..33387093da7 100644
--- a/src/plugins/texteditor/textdocumentlayout.h
+++ b/src/plugins/texteditor/textdocumentlayout.h
@@ -17,8 +17,9 @@
 
 namespace TextEditor {
 
-struct TEXTEDITOR_EXPORT Parenthesis
+class TEXTEDITOR_EXPORT Parenthesis
 {
+public:
     enum Type : char { Opened, Closed };
 
     Parenthesis() = default;