diff --git a/src/lib/syntaxhighlighter.cpp b/src/lib/syntaxhighlighter.cpp
--- a/src/lib/syntaxhighlighter.cpp
+++ b/src/lib/syntaxhighlighter.cpp
@@ -83,10 +83,8 @@
 
 void SyntaxHighlighter::setDefinition(const Definition &def)
 {
-    const auto needsRehighlight = definition() != def;
     AbstractHighlighter::setDefinition(def);
-    if (needsRehighlight)
-        rehighlight();
+    rehighlight();
 }
 
 bool SyntaxHighlighter::startsFoldingRegion(const QTextBlock &startBlock) const