diff --git a/src/render/katerenderer.cpp b/src/render/katerenderer.cpp
--- a/src/render/katerenderer.cpp
+++ b/src/render/katerenderer.cpp
@@ -384,6 +384,10 @@
 {
     QVector<QTextLayout::FormatRange> newHighlight;
 
+    if (textLine->length() > 1024 && !selectionsOnly) {
+        return newHighlight;
+    }
+
     // Don't compute the highlighting if there isn't going to be any highlighting
     QList<Kate::TextRange *> rangesWithAttributes = m_doc->buffer().rangesForLine(line, m_printerFriendly ? nullptr : m_view, true);
     if (selectionsOnly || !textLine->attributesList().isEmpty() || !rangesWithAttributes.isEmpty()) {