diff --git a/ffi.scm b/ffi.scm
index 3f2e553..051c2c2 100644
--- a/ffi.scm
+++ b/ffi.scm
@@ -1,52 +1,51 @@
 ;; FFI interface for TinySCHEME.
 ;;
 ;; Copyright (C) 2016 g10 Code GmbH
 ;;
 ;; This file is part of GnuPG.
 ;;
 ;; GnuPG is free software; you can redistribute it and/or modify
 ;; it under the terms of the GNU General Public License as published by
 ;; the Free Software Foundation; either version 3 of the License, or
 ;; (at your option) any later version.
 ;;
 ;; GnuPG is distributed in the hope that it will be useful,
 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 ;; GNU General Public License for more details.
 ;;
 ;; You should have received a copy of the GNU General Public License
 ;; along with this program; if not, see <http://www.gnu.org/licenses/>.
 
 ;; Foreign function wrapper.  Expects F to return a list with the
 ;; first element being the `error_t' value returned by the foreign
 ;; function.  The error is thrown, or the cdr of the result is
 ;; returned.
 (define (ffi-apply name f args)
   (let ((result (apply f args)))
     (cond
      ((string? result)
       (ffi-fail name args result))
      ((not (= (car result) 0))
       (ffi-fail name args (strerror (car result))))
      ((and (= (car result) 0) (pair? (cdr result))) (cadr result))
      ((= (car result) 0) '())
      (else
       (throw (list "Result violates FFI calling convention: " result))))))
 
 (define (ffi-fail name args message)
   (let ((args' (open-output-string)))
     (write (cons (string->symbol name) args) args')
-    (throw (string-append
-	    (get-output-string args') ": " message))))
+    (throw (get-output-string args') message)))
 
 ;; Pseudo-definitions for foreign functions.  Evaluates to no code,
 ;; but serves as documentation.
 (macro (ffi-define form))
 
 ;; Runtime support.
 
 ;; Low-level mechanism to terminate the process.
 (ffi-define (_exit status))
 
 ;; Get the current time in seconds since the epoch.
 (ffi-define (get-time))