diff --git a/scheme/completer.scm b/scheme/completer.scm
index 7fd1497..bb0c05d 100644
--- a/scheme/completer.scm
+++ b/scheme/completer.scm
@@ -144,13 +144,16 @@
 		   (list completed-line '() cursor-index to-complete parsed))))
               (else
                (let ((common-prefix (strings-common-prefix completions)))
-                 (call-with-values
-                     (lambda ()
-                       (unparse-command-line
-                        parsed (lambda (to-complete)
-                                 (display common-prefix))))
-                   (lambda (completed-line cursor-index)
-                     (list completed-line completions cursor-index to-complete parsed)))))))))))
+                 (debug-message "common-prefix is" common-prefix)
+                 (if (string=? common-prefix "")
+                     (list #f completions cursor-index to-complete parsed)
+                     (call-with-values
+                         (lambda ()
+                           (unparse-command-line
+                            parsed (lambda (to-complete)
+                                     (display common-prefix))))
+                       (lambda (completed-line cursor-index)
+                         (list completed-line completions cursor-index to-complete parsed))))))))))))
 
 
 (define (strings-common-prefix strs)
diff --git a/scheme/nuit-engine.scm b/scheme/nuit-engine.scm
index d1769c1..c214736 100644
--- a/scheme/nuit-engine.scm
+++ b/scheme/nuit-engine.scm
@@ -738,28 +738,30 @@
 	  ;; #### beep or so
 	  #f)
 	(destructure 
-	    (((completed-line completions cursor-index to-complete cmdln) completion-info))
-	  (cond
-	   ((null? completions)
-	    ;; #### don't ask
-	    (display-completed-line completed-line (+ 2 cursor-index))
-	    #f)
-	   ((list? completions)
-            (display-completed-line completed-line (+ 2 cursor-index))
-	    (let* ((select-list
-		    (completions->select-list 
-		     completions 
-		     (- (result-buffer-num-lines (result-buffer)) 3)))
-		   (selector
-		    (make-completion-selector select-list completions
-					      cmdln to-complete)))
-	      (paint-completion-select-list select-list command)
-	      (move-cursor (command-buffer) (result-buffer))
-	      (refresh-command-window)
-	      selector))
-	   (else
-	    (error "COMPLETE returned an unexpected value" 
-		   completions)))))))
+         (((maybe-completed-line completions cursor-index to-complete cmdln) completion-info))
+
+         (if maybe-completed-line 
+             ;; #### don't ask about the 2...
+             (display-completed-line maybe-completed-line (+ 2 cursor-index)))
+
+         (cond
+          ((null? completions)
+           #f)
+          ((list? completions)
+           (let* ((select-list
+                   (completions->select-list 
+                    completions 
+                    (- (result-buffer-num-lines (result-buffer)) 3)))
+                  (selector
+                   (make-completion-selector select-list completions
+                                             cmdln to-complete)))
+             (paint-completion-select-list select-list command)
+             (move-cursor (command-buffer) (result-buffer))
+             (refresh-command-window)
+             selector))
+          (else
+           (error "COMPLETE returned an unexpected value" 
+                  completions)))))))
 
 (define (make-completion-selector select-list completions 
 				  cmdln to-complete)