diff -r -U2 maxima-5.37.1.orig/src/db.lisp maxima-5.37.1/src/db.lisp
--- maxima-5.37.1.orig/src/db.lisp	2015-08-11 01:01:13.000000000 +0600
+++ maxima-5.37.1/src/db.lisp	2015-09-04 00:21:43.596685564 +0600
@@ -389,10 +389,14 @@
 
 (defmfun isp (pat)
-  (let ((isp 'unknown))
+  (let ((isp 'unknown) #+ccl (err t))
     (ignore-errors
       (setq isp
 	    (cond ((truep pat))
 		  ((falsep pat) nil)
-		  (t 'unknown))))
+		  (t 'unknown)))
+      (setq err nil))
+    #+ccl
+    (when err
+      (setq +labs nil))
     isp))