diff --git a/pkgs/racket-test/tests/json/json.rkt b/pkgs/racket-test/tests/json/json.rkt
index 612323ae50..bc566cb778 100644
--- a/pkgs/racket-test/tests/json/json.rkt
+++ b/pkgs/racket-test/tests/json/json.rkt
@@ -174,6 +174,7 @@
         (string->jsexpr " [\"x\",1, \"y\",2} ") =error> "string->jsexpr:"
         (string->jsexpr @T{ truelove }) =error> "string->jsexpr:"
         (string->jsexpr @T{ truebred }) =error> "string->jsexpr:"
+        (string->jsexpr @T{ truea }) =error> "string->jsexpr:"
         (string->jsexpr @T{ falsehood }) =error> "string->jsexpr:"
         (string->jsexpr @T{ falsetto }) =error> "string->jsexpr:"
         (string->jsexpr @T{ nullity }) =error> "string->jsexpr:"
diff --git a/racket/collects/json/main.rkt b/racket/collects/json/main.rkt
index 2eef74fe7a..93e4d85609 100644
--- a/racket/collects/json/main.rkt
+++ b/racket/collects/json/main.rkt
@@ -310,9 +310,9 @@
     ;; Check for delimiter, defined for our purposes as matching #rx"\\b":
     (define b (peek-byte i))
     (unless (eof-object? b)
-      (when (or (< (char->integer #\a) b (char->integer #\z))
-                (< (char->integer #\A) b (char->integer #\Z))
-                (< (char->integer #\0) b (char->integer #\9))
+      (when (or (<= (char->integer #\a) b (char->integer #\z))
+                (<= (char->integer #\A) b (char->integer #\Z))
+                (<= (char->integer #\0) b (char->integer #\9))
                 (eqv? b (char->integer #\_)))
         (bad-input bstr))))
   ;;