diff --git a/foreign/c/pointer.scm b/foreign/c/pointer.scm
index ce55abf..7d9baaa 100644
--- a/foreign/c/pointer.scm
+++ b/foreign/c/pointer.scm
@@ -77,10 +77,11 @@
 (define-syntax c-utf8->string
   (syntax-rules ()
     ((_ c-bytevector)
-     (when (c-null? c-bytevector)
-       (error "Can not turn null pointer into string" 'c-bytevector))
-     (let ((size (c-strlen c-bytevector)))
-       (utf8->string (c-bytevector->bytevector c-bytevector size))))))
+     (begin
+       (when (c-null? c-bytevector)
+         (error "Can not turn null pointer into string" 'c-bytevector))
+       (let ((size (c-strlen c-bytevector)))
+         (utf8->string (c-bytevector->bytevector c-bytevector size)))))))
 
 (define string->c-utf8
   (lambda (string-var)