diff --git a/tools/memory-model/lock.cat b/tools/memory-model/lock.cat
index 53b5a492739d..21ba65086938 100644
--- a/tools/memory-model/lock.cat
+++ b/tools/memory-model/lock.cat
@@ -102,19 +102,19 @@ let rf-lf = rfe-lf | rfi-lf
  * within one of the lock's critical sections returns False.
  *)
 
-(* rfi for RU events: an RU may read from the last po-previous UL *)
-let rfi-ru = ([UL] ; po-loc ; [RU]) \ ([UL] ; po-loc ; [LKW] ; po-loc)
-
-(* rfe for RU events: an RU may read from an external UL or the initial write *)
-let all-possible-rfe-ru =
-	let possible-rfe-ru r =
+(*
+ * rf for RU events: an RU may read from an external UL or the initial write,
+ * or from the last po-previous UL
+ *)
+let all-possible-rf-ru =
+	let possible-rf-ru r =
 		let pair-to-relation p = p ++ 0
-		in map pair-to-relation (((UL | IW) * {r}) & loc & ext)
-	in map possible-rfe-ru RU
+		in map pair-to-relation ((((UL | IW) * {r}) & loc & ext) |
+			(((UL * {r}) & po-loc) \ ([UL] ; po-loc ; [LKW] ; po-loc)))
+	in map possible-rf-ru RU
 
 (* Generate all rf relations for RU events *)
-with rfe-ru from cross(all-possible-rfe-ru)
-let rf-ru = rfe-ru | rfi-ru
+with rf-ru from cross(all-possible-rf-ru)
 
 (* Final rf relation *)
 let rf = rf | rf-lf | rf-ru