diff --git a/collects/htdp/convert.rkt b/collects/htdp/convert.rkt
index e5e29808cb..9c58db1d62 100644
--- a/collects/htdp/convert.rkt
+++ b/collects/htdp/convert.rkt
@@ -237,12 +237,12 @@
 ;; convert-file : str (num -> num) str -> void
 ;; to read a number from file in, to convert it with f, and to write it to out
 (define (convert-file in f out)
-  (check-arg 'convert-file (string? in) "string" "first" in)
+  (check-arg 'convert-file (path-string? in) "string" "first" in)
   (check-arg 'convert-file (file-exists? in) 
              (format "name of existing file in ~a" (current-directory))
              "first" in)
   (check-proc 'convert-file f 1 "convert-file" "one argument")
-  (check-arg 'convert-file (string? out) "string" "third" out)
+  (check-arg 'convert-file (path-string? out) "string" "third" out)
   ;; [ -> Void] -> Void 
   ;; perform the actual conversion on the file after optionally reading a prelude 
   (define (convert-file prefix)
diff --git a/collects/htdp/tests/convert-drracket-error.rkt b/collects/htdp/tests/convert-drracket-error.rkt
index e9602818e7..5a7aa95fd7 100644
--- a/collects/htdp/tests/convert-drracket-error.rkt
+++ b/collects/htdp/tests/convert-drracket-error.rkt
@@ -1,12 +1,15 @@
 #lang racket
+(require racket/runtime-path
+         htdp/convert)
 
-(require htdp/convert)
+(define-runtime-path non-error-pth "convert-drracket-non-error.txt")
+(define-runtime-path error-pth "convert-drracket-error.txt")
 
 (define (Fahrenheit->Celsius x) (* (/ 100 180) (- x 32)))
 
-(convert-file "convert-drracket-non-error.txt" Fahrenheit->Celsius "out.dat")
+(convert-file non-error-pth Fahrenheit->Celsius "out.dat")
 
 (with-handlers ((exn:fail:read? void))
   "The input file contains a bad header. The next line should raise an exn."
-  (convert-file "convert-drracket-error.txt" Fahrenheit->Celsius "out.dat")
+  (convert-file error-pth Fahrenheit->Celsius "out.dat")
   (raise `(test "this test should have failed but didn't")))