diff --git a/collects/parser-tools/lex.rkt b/collects/parser-tools/lex.rkt
index 6f1c3ca..d711808 100644
--- a/collects/parser-tools/lex.rkt
+++ b/collects/parser-tools/lex.rkt
@@ -294,9 +294,9 @@
                                               longest-match-length)))))))))))))
       (lambda (ip)
         (unless (input-port? ip)
-          (raise-type-error 
+          (raise-argument-error 
            'lexer 
-           "input-port"
+           "input-port?"
            0
            ip))
         (lexer ip))))
diff --git a/collects/parser-tools/yacc.rkt b/collects/parser-tools/yacc.rkt
index 5e2af6a..efb1900 100644
--- a/collects/parser-tools/yacc.rkt
+++ b/collects/parser-tools/yacc.rkt
@@ -224,10 +224,10 @@
        (values tok #f v1 v2))
       ((token? tok)
        (values (real-token-name tok) (real-token-value tok) v1 v2))
-      (else (raise-type-error 'parser 
-                              "symbol or struct:token"
-                              0 
-                              tok))))
+      (else (raise-argument-error 'parser 
+                                  "(or/c symbol? token?)"
+                                  0 
+                                  tok))))
   
   ;; extract-src-pos : position-token -> symbol any any any
   (define (extract-src-pos ip)
@@ -237,10 +237,10 @@
                        (position-token-start-pos ip)
                        (position-token-end-pos ip)))
       (else
-       (raise-type-error 'parser 
-                         "struct:position-token"
-                         0
-                         ip))))
+       (raise-argument-error 'parser 
+                             "position-token?"
+                             0
+                             ip))))
   
   ;; extract-no-src-pos : (symbol or make-token) -> symbol any any any
   (define (extract-no-src-pos ip)