diff --git a/guix/ui.scm b/guix/ui.scm
index cd47989ca6..370b41b9dc 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -77,17 +77,19 @@ (define-syntax name
       (define (augmented-format-string fmt)
         (string-append "~:[~*~;guix ~a: ~]~a" (syntax->datum fmt)))
 
-      (syntax-case x (N_ _)                    ; these are literals, yeah...
-        ((name (_ fmt) args (... ...))
-         (string? (syntax->datum #'fmt))
+      (syntax-case x ()
+        ((name (underscore fmt) args (... ...))
+         (and (string? (syntax->datum #'fmt))
+              (free-identifier=? #'underscore #'_))
          (with-syntax ((fmt*   (augmented-format-string #'fmt))
                        (prefix (datum->syntax x prefix)))
            #'(format (guix-warning-port) (gettext fmt*)
                      (program-name) (program-name) prefix
                      args (... ...))))
-        ((name (N_ singular plural n) args (... ...))
+        ((name (N-underscore singular plural n) args (... ...))
          (and (string? (syntax->datum #'singular))
-              (string? (syntax->datum #'plural)))
+              (string? (syntax->datum #'plural))
+              (free-identifier=? #'N-underscore #'N_))
          (with-syntax ((s      (augmented-format-string #'singular))
                        (p      (augmented-format-string #'plural))
                        (prefix (datum->syntax x prefix)))