diff --git a/format.rkt b/format.rkt
index 6afa445..2554594 100644
--- a/format.rkt
+++ b/format.rkt
@@ -4,7 +4,7 @@
 
 (provide
   format:
-  ;; (-> (x:String) Any *N Void)
+  ;; (-> (x#:String) Any *N Void)
   ;; Takes 1 required string argument and N additional arguments,
   ;;  where N is the number of format sequences in the string.
   ;;
@@ -19,90 +19,6 @@
 )
 
 (require
-  (for-syntax
-    trivial/private/common
-    typed/racket/base
-    syntax/parse))
-
-;; =============================================================================
-
-(begin-for-syntax
-  ;; Count the number of format escapes in a string.
-  ;; Returns a list of optional types (to be spliced into the source code).
-  ;;   Example: If result is '(#f Integer), then
-  ;;   - The format string expects 2 arguments
-  ;;   - First argument has no type constraints, second must be an Integer
-  (define (format-parser stx)
-    (define str (if (string? (syntax-e stx)) (syntax-e stx) (quoted-stx-value? stx)))
-    (cond
-     [(string? str)
-      (define last-index (- (string-length str) 1))
-      (let loop ([i 0] [acc '()])
-        (cond
-         [(>= i last-index)
-          (reverse acc)]
-         [(eq? #\~ (string-ref str i))
-          ;; From fprintf docs @ http://docs.racket-lang.org/reference/Writing.html
-          (case (string-ref str (+ i 1))
-           [(#\% #\n #\~ #\space #\tab #\newline)
-            ;; Need 0 arguments
-            (loop (+ i 2) acc)]
-           [(#\a #\A #\s #\S #\v #\V #\e #\E)
-            ;; Need 1 argument, can be anything
-            (loop (+ i 2) (cons #f acc))]
-           [(#\.)
-            ;; Need at most 1, can be anything
-            (if (and (< (+ 1 i) last-index)
-                     (memq (string-ref str (+ i 2)) '(#\a #\A #\s #\S #\v #\V)))
-              (loop (+ i 3) (cons #f acc))
-              (loop (+ i 3) acc))]
-           [(#\c #\C)
-            ;; Need 1 `char?`
-            (loop (+ i 2) (cons (syntax/loc stx Char) acc))]
-           [(#\b #\B #\o #\O #\x #\X)
-            ;; Need 1 `exact?`
-            (loop (+ i 2) (cons (syntax/loc stx Exact-Number) acc))]
-           [else
-            ;; Invalid format sequence
-            (raise-user-error "format: unrecognized pattern string '~~~c'"
-              (string-ref str (+ i 1)))])]
-         [else
-          (loop (+ i 1) acc)]))]
-     [else #f]))
-
-  (define-values (
-    _key
-    fmt?
-    _define
-    _let
-   ) (make-value-property 'string:format format-parser))
-
-  (define-syntax-class/predicate string/format fmt?)
-)
-
-;; -----------------------------------------------------------------------------
-
-(define-syntax format: (make-alias #'format
-  (lambda (stx) (syntax-parse stx
-   [(_ fmt:string/format arg* ...)
-    ;; -- 1. Parse expected types from the template
-    #:when (let ([num-expected (length (syntax-e #'fmt.evidence))]
-                 [num-given (length (syntax-e #'(arg* ...)))])
-             (unless (= num-expected num-given)
-               (apply raise-arity-error
-                 'format:
-                 num-expected
-                 (map syntax->datum (syntax-e #'(arg* ...))))))
-    ;; -- 2. If any types left obligations, use `ann` to typecheck the args
-    #:with (arg+* ...)
-      (for/list ([a (in-list (syntax-e #'(arg* ...)))]
-                 [t (in-list (syntax-e #'fmt.evidence))])
-        (if (syntax-e t) (quasisyntax/loc stx (ann #,a #,t)) a))
-    (syntax/loc stx (format fmt.expanded arg+* ...))]
-   [_ #f]))))
-
-(define-syntax printf: (make-alias #'printf
-  (lambda (stx) (syntax-parse stx
-   [(_ arg* ...)
-    (syntax/loc stx (display (format: arg* ...)))]
-   [_ #f]))))
+  (only-in trivial/private/format
+    format:
+    printf:))
diff --git a/private/format.rkt b/private/format.rkt
new file mode 100644
index 0000000..7d16dee
--- /dev/null
+++ b/private/format.rkt
@@ -0,0 +1,98 @@
+#lang typed/racket/base
+
+;; Statically-checked format strings
+
+(provide
+  format:
+  printf:
+)
+
+(require
+  (for-syntax
+    trivial/private/common
+    typed/racket/base
+    syntax/parse))
+
+;; =============================================================================
+
+(begin-for-syntax
+  ;; Count the number of format escapes in a string.
+  ;; Returns a list of optional types (to be spliced into the source code).
+  ;;   Example: If result is '(#f Integer), then
+  ;;   - The format string expects 2 arguments
+  ;;   - First argument has no type constraints, second must be an Integer
+  (define (format-parser stx)
+    (define str (if (string? (syntax-e stx)) (syntax-e stx) (quoted-stx-value? stx)))
+    (cond
+     [(string? str)
+      (define last-index (- (string-length str) 1))
+      (let loop ([i 0] [acc '()])
+        (cond
+         [(>= i last-index)
+          (reverse acc)]
+         [(eq? #\~ (string-ref str i))
+          ;; From fprintf docs @ http://docs.racket-lang.org/reference/Writing.html
+          (case (string-ref str (+ i 1))
+           [(#\% #\n #\~ #\space #\tab #\newline)
+            ;; Need 0 arguments
+            (loop (+ i 2) acc)]
+           [(#\a #\A #\s #\S #\v #\V #\e #\E)
+            ;; Need 1 argument, can be anything
+            (loop (+ i 2) (cons #f acc))]
+           [(#\.)
+            ;; Need at most 1, can be anything
+            (if (and (< (+ 1 i) last-index)
+                     (memq (string-ref str (+ i 2)) '(#\a #\A #\s #\S #\v #\V)))
+              (loop (+ i 3) (cons #f acc))
+              (loop (+ i 3) acc))]
+           [(#\c #\C)
+            ;; Need 1 `char?`
+            (loop (+ i 2) (cons (syntax/loc stx Char) acc))]
+           [(#\b #\B #\o #\O #\x #\X)
+            ;; Need 1 `exact?`
+            (loop (+ i 2) (cons (syntax/loc stx Exact-Number) acc))]
+           [else
+            ;; Invalid format sequence
+            (raise-user-error "format: unrecognized pattern string '~~~c'"
+              (string-ref str (+ i 1)))])]
+         [else
+          (loop (+ i 1) acc)]))]
+     [else #f]))
+
+  (define-values (
+    _key
+    fmt?
+    _define
+    _let
+   ) (make-value-property 'string:format format-parser))
+
+  (define-syntax-class/predicate string/format fmt?)
+)
+
+;; -----------------------------------------------------------------------------
+
+(define-syntax format: (make-alias #'format
+  (lambda (stx) (syntax-parse stx
+   [(_ fmt:string/format arg* ...)
+    ;; -- 1. Parse expected types from the template
+    #:when (let ([num-expected (length (syntax-e #'fmt.evidence))]
+                 [num-given (length (syntax-e #'(arg* ...)))])
+             (unless (= num-expected num-given)
+               (apply raise-arity-error
+                 'format:
+                 num-expected
+                 (map syntax->datum (syntax-e #'(arg* ...))))))
+    ;; -- 2. If any types left obligations, use `ann` to typecheck the args
+    #:with (arg+* ...)
+      (for/list ([a (in-list (syntax-e #'(arg* ...)))]
+                 [t (in-list (syntax-e #'fmt.evidence))])
+        (if (syntax-e t) (quasisyntax/loc stx (ann #,a #,t)) a))
+    (syntax/loc stx (format fmt.expanded arg+* ...))]
+   [_ #f]))))
+
+(define-syntax printf: (make-alias #'printf
+  (lambda (stx) (syntax-parse stx
+   [(_ arg* ...)
+    (syntax/loc stx (display (format: arg* ...)))]
+   [_ #f]))))
+