diff --git a/src/libs/utils/textutils.cpp b/src/libs/utils/textutils.cpp
index d102de794ad..f72dd89321c 100644
--- a/src/libs/utils/textutils.cpp
+++ b/src/libs/utils/textutils.cpp
@@ -142,6 +142,9 @@ QTextCursor wordStartCursor(const QTextCursor &textCursor)
 
 int utf8NthLineOffset(const QTextDocument *textDocument, const QByteArray &buffer, int line)
 {
+    if (textDocument->blockCount() < line)
+        return -1;
+
     if (textDocument->characterCount() == buffer.size() + 1)
         return textDocument->findBlockByNumber(line - 1).position();