diff --git a/collects/r6rs/private/readtable.ss b/collects/r6rs/private/readtable.ss
index a8a518b1cd..b7334f3d9c 100644
--- a/collects/r6rs/private/readtable.ss
+++ b/collects/r6rs/private/readtable.ss
@@ -3,6 +3,7 @@
 ;; Readtable-based R6RS reading
 
 (require syntax/readerr
+         scheme/promise
          (for-syntax scheme/base))
 
 (provide with-r6rs-reader-parameters
@@ -436,8 +437,8 @@
                        (num 8)
                        (num 2)))
 
-    (values (pregexp (string-append "^" identifier "$"))
-            (pregexp (string-append "^" number "$")))))
+    (values (delay (pregexp (string-append "^" identifier "$")))
+            (delay (pregexp (string-append "^" number "$"))))))
 
 (define (do-read-symbol-or-number num? prefix port src line col pos)
   ;; Read a delimited sequence (using an extended notion of delimiter),
@@ -453,7 +454,7 @@
      [(regexp-match? #rx"^[a-zA-Z!$%&*/:<=>?^_~][a-zA-Z0-9+!$%&*/:<=>?^_~.@-]*$" thing)
       ;; Simple symbol:
       (string->symbol thing)]
-     [(regexp-match? rx:number thing)
+     [(regexp-match? (force rx:number) thing)
       (let ([n (string->number 
                 ;; MzScheme doesn't handle mantissa widths, yet, so strip them out:
                 (regexp-replace* #rx"[|][0-9]+" thing ""))])
@@ -461,7 +462,7 @@
           (error 'r6rs-parser "number didn't convert: ~e" thing))
         n)]
      [(and (not num?)
-           (regexp-match? rx:id thing))
+           (regexp-match? (force rx:id) thing))
       (string->symbol
        (bytes->string/utf-8 
         (let loop ([t (string->bytes/utf-8 thing)])
diff --git a/collects/rnrs/base-6.ss b/collects/rnrs/base-6.ss
index 1ba57a14d3..0c7b240f08 100644
--- a/collects/rnrs/base-6.ss
+++ b/collects/rnrs/base-6.ss
@@ -3,6 +3,7 @@
 (require (for-syntax (rename-in r6rs/private/base-for-syntax
                                 [syntax-rules r6rs:syntax-rules])
                      scheme/base)
+         scheme/promise
          scheme/splicing
          r6rs/private/qq-gen
          r6rs/private/exns
@@ -346,7 +347,7 @@
          [s (if (regexp-match? #rx"#[dDxXoObB]" s)
                 s
                 (string-append prefix s))])
-    (and (regexp-match? rx:number s)
+    (and (regexp-match? (force rx:number) s)
          (string->number (regexp-replace* #rx"[|][0-9]+" s "")))))
 
 (define r6rs:symbol=?