diff --git a/foreign/c/pointer.scm b/foreign/c/pointer.scm
index ed82702..ce55abf 100644
--- a/foreign/c/pointer.scm
+++ b/foreign/c/pointer.scm
@@ -74,12 +74,13 @@
   (lambda (bytevector-var)
     (c-strlen bytevector-var)))
 
-(define c-utf8->string
-  (lambda (c-bytevector)
-    (when (c-null? c-bytevector)
-      (error "Can not turn null pointer into string"))
-    (let ((size (c-strlen c-bytevector)))
-      (utf8->string (c-bytevector->bytevector c-bytevector size)))))
+(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))))))
 
 (define string->c-utf8
   (lambda (string-var)