diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/SideBySide.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/SideBySide.java
index 5934c5d992..9566a0b559 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/SideBySide.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/SideBySide.java
@@ -894,12 +894,59 @@ public class SideBySide extends Screen {
     };
   }
 
+  private int adjustCommitMessageLine(int line) {
+    /* When commit messages are shown in the side-by-side screen they include
+      a header block that looks like this:
+
+      1 Parent:     deadbeef (Parent commit title)
+      2 Author:     A. U. Thor <author@example.com>
+      3 AuthorDate: 2015-02-27 19:20:52 +0900
+      4 Commit:     A. U. Thor <author@example.com>
+      5 CommitDate: 2015-02-27 19:20:52 +0900
+      6 [blank line]
+      7 Commit message title
+      8
+      9 Commit message body
+     10 ...
+     11 ...
+
+    If the commit is a merge commit, both parent commits are listed in the
+    first two lines instead of a 'Parent' line:
+
+      1 Merge Of:   deadbeef (Parent 1 commit title)
+      2             beefdead (Parent 2 commit title)
+
+    */
+
+    // Offset to compensate for header lines until the blank line
+    // after 'CommitDate'
+    int offset = 6;
+
+    // Adjust for merge commits, which have two parent lines
+    if (diff.text_b().startsWith("Merge")) {
+      offset += 1;
+    }
+
+    // If the cursor is inside the header line, reset to the first line of the
+    // commit message. Otherwise if the cursor is on an actual line of the commit
+    // message, adjust the line number to compensate for the header lines, so the
+    // focus is on the correct line.
+    if (line <= offset) {
+      return 1;
+    } else {
+      return line - offset;
+    }
+  }
+
   private Runnable modifyInEditScreen(final CodeMirror cm) {
     return new Runnable() {
       @Override
       public void run() {
         LineHandle handle = cm.extras().activeLine();
         int line = cm.getLineNumber(handle) + 1;
+        if (Patch.COMMIT_MSG.equals(path)) {
+          line = adjustCommitMessageLine(line);
+        }
         String token = Dispatcher.toEditScreen(revision, path, line);
         if (!Gerrit.isSignedIn()) {
           Gerrit.doSignIn(token);