diff --git a/app/assets/javascripts/diffs/store/mutations.js b/app/assets/javascripts/diffs/store/mutations.js
index 370073f10333ca6e13acf8eac56ef1c6ec69449c..2cc2e13648f6c8323ec4bc21fb9801f8a98dfc19 100644
--- a/app/assets/javascripts/diffs/store/mutations.js
+++ b/app/assets/javascripts/diffs/store/mutations.js
@@ -210,6 +210,8 @@ export default {
 
     if (diffLines.length && positionType !== FILE_DIFF_POSITION_TYPE) {
       const line = diffLines.find(isTargetLine);
+      // skip if none of the discussion positions matched a diff position
+      if (!line) return;
       const discussions = addDiscussion(line.discussions || []);
       Object.assign(line, {
         discussions,