diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchScreen.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchScreen.java
index 0cdfcc8..c815097 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchScreen.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchScreen.java
@@ -479,6 +479,9 @@
   public void setSideA(PatchSet.Id patchSetId) {
     idSideA = patchSetId;
     diffSideA = patchSetId;
+    if (fileList != null) {
+      fileList.setPatchSetIdToCompareWith(patchSetId);
+    }
   }
 
   public void setSideB(PatchSet.Id patchSetId) {