diff --git a/pkgs/compiler-pkgs/compiler-lib/compiler/commands/decompile.rkt b/pkgs/compiler-pkgs/compiler-lib/compiler/commands/decompile.rkt
index 004693fc5a..57b7f55af0 100644
--- a/pkgs/compiler-pkgs/compiler-lib/compiler/commands/decompile.rkt
+++ b/pkgs/compiler-pkgs/compiler-lib/compiler/commands/decompile.rkt
@@ -3,25 +3,80 @@
          raco/command-name
          compiler/zo-parse
          compiler/decompile
-         racket/pretty)
+         racket/pretty
+         racket/format)
+
+(define (get-name)
+  (string->symbol (short-program+command-name)))
+
+(define force? #f)
 
 (define source-files
   (command-line
    #:program (short-program+command-name)
    #:once-each
+   [("--force") "Ignore timestamp mimatch on associated \".zo\""
+    (set! force? #t)]
    [("--columns" "-n") n "Format for <n> columns"
     (let ([num (string->number n)])
       (unless (exact-positive-integer? num)
-        (raise-user-error (string->symbol (short-program+command-name))
+        (raise-user-error (get-name)
                           "not a valid column count: ~a" n))
       (pretty-print-columns num))]
    #:args source-or-bytecode-file
    source-or-bytecode-file))
 
+(define (check-files orig-file alt-file)
+  (cond
+   [(not (file-exists? alt-file))
+    (cond
+     [(file-exists? orig-file)
+      (unless (is-bytecode-file? orig-file)
+        (raise-user-error (get-name)
+                          (~a "not a bytecode file, and no associated \".zo\" file\n"
+                              "  path: ~a\n"
+                              "  tried associated path: ~a")
+                          orig-file
+                          alt-file))]
+     [else
+      (raise-user-error (get-name)
+                        (~a "no such file, and no associated \".zo\" file\n"
+                            "  path: ~a\n"
+                            "  tried associated path: ~a")
+                        orig-file
+                        alt-file)])]
+   [(not (is-bytecode-file? alt-file))
+    (raise-user-error (get-name)
+                      (~a "associated \".zo\" file is not a bytecode file\n"
+                          "  original path: ~a\n"
+                          "  associated path: ~a")
+                      orig-file
+                      alt-file)]
+   [(and (not force?)
+         ((file-or-directory-modify-seconds orig-file)
+          . > .
+          (file-or-directory-modify-seconds alt-file)))
+    ;; return a warning:
+    (raise-user-error (get-name)
+                      (~a "associated \".zo\" file's date is older than given file's date;\n"
+                          " consider using `raco make` to rebuild the source file, or use `--force`\n"
+                          " to skip the date check\n"
+                          "  original path: ~a\n"
+                          "  associated path: ~a")
+                      orig-file
+                      alt-file)]))
+
+(define (is-bytecode-file? orig-file)
+  (call-with-input-file*
+   orig-file
+   (lambda (i)
+     (equal? #"#~" (read-bytes 2 i)))))
+
 (for ([zo-file source-files])
   (let ([zo-file (path->complete-path zo-file)])
     (let-values ([(base name dir?) (split-path zo-file)])
       (let ([alt-file (build-path base "compiled" (path-add-suffix name #".zo"))])
+        (check-files zo-file alt-file)
         (parameterize ([current-load-relative-directory base]
                        [print-graph #t])
           (pretty-write