diff --git a/src/Refinements/Expr.class.st b/src/Refinements/Expr.class.st
index 584cb70da..b81429086 100644
--- a/src/Refinements/Expr.class.st
+++ b/src/Refinements/Expr.class.st
@@ -101,6 +101,13 @@ Expr >> <+ rhs [
 		sort: Bool sort
 ]
 
+{ #category : #'theory symbols' }
+Expr >> <= rhs [
+	^ECst
+		expr: (EMessageSend of: (MessageSend receiver: self selector: #<= argument: rhs))
+		sort: Bool sort
+]
+
 { #category : #'theory symbols' }
 Expr >> <=> rhs [
 	^ECst