--- gnus/lisp/mailcap.el.orig	2006-01-31 02:11:48.000000000 +0100
+++ gnus/lisp/mailcap.el	2006-07-28 17:54:39.000000000 +0200
@@ -647,11 +647,11 @@
     (cond ((setq cache (assoc test mailcap-viewer-test-cache))
 	   (cadr cache))
 	  ((not test-info) t)		; No test clause
+	  ((not test) nil)		; Already failed test
 	  (t
 	   (setq
 	    result
 	    (cond
-	     ((not test) nil)		; Already failed test
 	     ((eq test t) t)		; Already passed test
 	     ((functionp test)		; Lisp function as test
 	      (funcall test type-info))