diff --git a/ansi-tests/decf.lsp b/ansi-tests/decf.lsp
index 4c1888998abc4c1f1bcd5eafa9106a3d951c1061..03093b3505727460cd2af4ecea6f8ab7ad710d7e 100644
--- a/ansi-tests/decf.lsp
+++ b/ansi-tests/decf.lsp
@@ -96,9 +96,10 @@
 	nconc
 	(loop for r = (random-from-interval 1000000)
 	      repeat 100
-	      unless (let* ((y x) (z (decf y r)))
-			(and (eql (- x r) y) (eql y z)))
-	      collect (list x y r)))
+	      when (let* ((y x) (z (decf y r)))
+			(and (not (and (eql (- x r) y) (eql y z)))
+			     (list x y r)))
+	      collect it))
   nil)
 
 (deftest decf.14
diff --git a/ansi-tests/incf.lsp b/ansi-tests/incf.lsp
index 4f826bffd7e5a435c37d1870a8aade16a48c699d..c5efd343ec0e0141e7a97be7356faea4122caeb8 100644
--- a/ansi-tests/incf.lsp
+++ b/ansi-tests/incf.lsp
@@ -96,9 +96,10 @@
 	nconc
 	(loop for r = (random-from-interval 1000000)
 	      repeat 100
-	      unless (let* ((y x) (z (incf y r)))
-			(and (eql (+ x r) y) (eql y z)))
-	      collect (list x y r)))
+	      when (let* ((y x) (z (incf y r)))
+			(and (not (and (eql (+ x r) y) (eql y z)))
+			     (list x y r)))
+	      collect it))
   nil)
 
 (deftest incf.14