diff --git a/src/render/katerenderer.cpp b/src/render/katerenderer.cpp
--- a/src/render/katerenderer.cpp
+++ b/src/render/katerenderer.cpp
@@ -384,19 +384,26 @@
 {
     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()) {
         RenderRangeList renderRanges;
 
-        // Add the inbuilt highlighting to the list
-        NormalRenderRange *inbuiltHighlight = new NormalRenderRange();
-        const QVector<Kate::TextLineData::Attribute> &al = textLine->attributesList();
-        for (int i = 0; i < al.count(); ++i)
-            if (al[i].length > 0 && al[i].attributeValue > 0) {
-                inbuiltHighlight->addRange(new KTextEditor::Range(KTextEditor::Cursor(line, al[i].offset), al[i].length), specificAttribute(al[i].attributeValue));
+        if (textLine->length() <= 1024) {
+            // Add the inbuilt highlighting to the list
+            NormalRenderRange *inbuiltHighlight = new NormalRenderRange();
+            const QVector<Kate::TextLineData::Attribute> &al = textLine->attributesList();
+            for (int i = 0; i < al.count(); ++i) {
+                if (al[i].length > 0 && al[i].attributeValue > 0) {
+                    inbuiltHighlight->addRange(new KTextEditor::Range(KTextEditor::Cursor(line, al[i].offset), al[i].length), specificAttribute(al[i].attributeValue));
+                }
             }
-        renderRanges.append(inbuiltHighlight);
+            renderRanges.append(inbuiltHighlight);
+        }
 
         if (!completionHighlight) {
             // check for dynamic hl stuff