diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 9131b74df..950222812 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -799,7 +799,7 @@ static void opServe(Strings opFlags, Strings opArgs)
         if (GET_PROTOCOL_MINOR(clientVersion) >= 3) {
             settings.buildRepeat = readInt(in);
             settings.enforceDeterminism = readInt(in);
-            settings.runDiffHook = readInt(in);
+            settings.runDiffHook = true;
         }
         settings.printRepeatedBuilds = false;
     };