diff --git a/pkgs/racket-test-core/tests/racket/rx.rktl b/pkgs/racket-test-core/tests/racket/rx.rktl
index 1b19cf8578..077bd52915 100644
--- a/pkgs/racket-test-core/tests/racket/rx.rktl
+++ b/pkgs/racket-test-core/tests/racket/rx.rktl
@@ -1605,6 +1605,19 @@
        (#"^(E)?(?(1)aa|a)*$" #"aaa" (#"aaa" #f))
        (#"^(E)?(?(1)aa|a)*$" #"aaaa" (#"aaaa" #f))))
 
+
+(let ()
+  (define out (open-output-bytes))
+  (define infinite-voids
+    (make-input-port
+     'voids
+     (lambda (s) (lambda args 'void))
+     (lambda (skip s evt) (lambda args 'void))
+     void))
+  (err/rt-test (regexp-match #rx"." infinite-voids)
+               exn:fail:contract?
+               #rx"non-character in an unsupported context"))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;  Test unicode-property patterns
 
diff --git a/pkgs/racket-test/tests/file/unzip.rkt b/pkgs/racket-test/tests/file/unzip.rkt
index 7cfeddc775..ddba603fc2 100644
--- a/pkgs/racket-test/tests/file/unzip.rkt
+++ b/pkgs/racket-test/tests/file/unzip.rkt
@@ -1,5 +1,6 @@
 #lang racket/base
 (require file/unzip
+         file/gunzip
          racket/runtime-path
          racket/port
          tests/eli-tester)
@@ -27,7 +28,18 @@
   (call-with-input-file* unzip-me.zip test-with-unzip)
   (call-with-input-file* unzip-me.zip
                          (lambda(in_port) (test-with-unzip (input-port-append #f in_port))))
-  (test-with-unzip-entry))
+  (test-with-unzip-entry)
+
+  (test (let ()
+          (define out (open-output-bytes))
+          (define infinite-voids
+            (make-input-port
+             'voids
+             (lambda (s) (lambda args 'void))
+             (lambda (skip s evt) (lambda args 'void))
+             void))
+          (inflate infinite-voids out))
+        =error> "non-character in an unsupported context"))
 
 (provide tests)
 (module+ main (tests))
diff --git a/racket/collects/file/gunzip.rkt b/racket/collects/file/gunzip.rkt
index 8732da0962..01d64155df 100644
--- a/racket/collects/file/gunzip.rkt
+++ b/racket/collects/file/gunzip.rkt
@@ -288,13 +288,18 @@
             (set! buf-pos (min MAX-LOOKAHEAD buf-max)))
           ;; Peek (not read) some available bytes:
           (let ([got (peek-bytes-avail! buffer buf-pos #f input-port buf-pos BUFFER-SIZE)])
-            (if (eof-object? got)
-                ;; Treat an EOF as a -1 "byte":
-                (begin
-                  (bytes-set! buffer buf-pos 255)
-                  (set! buf-max (add1 buf-pos)))
-                ;; Got normal bytes:
-                (set! buf-max (+ buf-pos got))))
+            (cond
+              [(eof-object? got)
+               ;; Treat an EOF as a -1 "byte":
+               (bytes-set! buffer buf-pos 255)
+               (set! buf-max (add1 buf-pos))]
+              [(fixnum? got)
+               ;; Got normal bytes:
+               (set! buf-max (+ buf-pos got))]
+              [else
+               (raise-arguments-error 'inflate
+                                      "non-character in an unsupported context"
+                                      "port" input-port)]))
           (READBITS n))
         (let ([v (bytes-ref buffer buf-pos)])
           (set! buf-pos (add1 buf-pos))
diff --git a/racket/src/cs/schemified/regexp.scm b/racket/src/cs/schemified/regexp.scm
index e0b043cba3..70735b2ca8 100644
--- a/racket/src/cs/schemified/regexp.scm
+++ b/racket/src/cs/schemified/regexp.scm
@@ -5028,13 +5028,19 @@
                               len_0))))))
                   (if (eof-object? n_0)
                     #f
-                    (if (zero? n_0)
-                      (begin (set-lazy-bytes-failed?! s_0 #t) #f)
-                      (begin
-                        (set-lazy-bytes-end!
-                         s_0
-                         (+ n_0 len_0 discarded-count_0))
-                        #t))))
+                    (if (not (fixnum? n_0))
+                      (raise-arguments-error
+                       'regexp-match
+                       "non-character in an unsupported context"
+                       "port"
+                       (lazy-bytes-in s_0))
+                      (if (zero? n_0)
+                        (begin (set-lazy-bytes-failed?! s_0 #t) #f)
+                        (begin
+                          (set-lazy-bytes-end!
+                           s_0
+                           (+ n_0 len_0 discarded-count_0))
+                          #t)))))
                 (let ((max-peek_0 (lazy-bytes-max-peek s_0)))
                   (let ((prefix-len_0
                          (if max-peek_0 (lazy-bytes-prefix-len s_0) #f)))
diff --git a/racket/src/regexp/match/lazy-bytes.rkt b/racket/src/regexp/match/lazy-bytes.rkt
index afdd36357b..4e11226087 100644
--- a/racket/src/regexp/match/lazy-bytes.rkt
+++ b/racket/src/regexp/match/lazy-bytes.rkt
@@ -113,6 +113,10 @@
                  len))
       (cond
        [(eof-object? n) #f]
+       [(not (fixnum? n))
+        (raise-arguments-error 'regexp-match
+                               "non-character in an unsupported context"
+                               "port" (lazy-bytes-in s))]
        [(zero? n)
         ;; would block or progress evt became ready
         (set-lazy-bytes-failed?! s #t)