diff --git a/collects/compiler/commands/make.rkt b/collects/compiler/commands/make.rkt
index 03dd574409..74f2b85ae7 100644
--- a/collects/compiler/commands/make.rkt
+++ b/collects/compiler/commands/make.rkt
@@ -16,6 +16,8 @@
 (define assume-primitives (make-parameter #t))
 (define worker-count (make-parameter 1))
 
+(define mzc-symbol (string->symbol (short-program+command-name)))
+
 (define source-files
   (command-line
    #:program (short-program+command-name)
@@ -67,9 +69,9 @@
                           (printf "  making ~s\n" (path->string p))))])
         (for ([file source-files])
           (unless (file-exists? file)
-            (error 'mzc "file does not exist: ~a" file))
+            (error mzc-symbol "file does not exist: ~a" file))
           (set! did-one? #f)
-          (let ([name (extract-base-filename/ss file 'mzc)])
+          (let ([name (extract-base-filename/ss file mzc-symbol)])
             (when (verbose)
               (printf "\"~a\":\n" file))
             (parameterize ([compile-context-preservation-enabled
diff --git a/collects/compiler/commands/pack.rkt b/collects/compiler/commands/pack.rkt
index 8a2fa32a50..db68d62889 100644
--- a/collects/compiler/commands/pack.rkt
+++ b/collects/compiler/commands/pack.rkt
@@ -19,6 +19,8 @@
 (define plt-setup-collections (make-parameter null))
 (define plt-include-compiled (make-parameter #f))
 
+(define mzc-symbol (string->symbol (short-program+command-name)))
+
 (define-values (plt-output source-files)
   (command-line
    #:program (short-program+command-name)
@@ -53,7 +55,7 @@
     (begin
       (for ([fd source-files])
         (unless (relative-path? fd)
-          (error 'mzc
+          (error mzc-symbol
                  "file/directory is not relative to the current directory: \"~a\""
                  fd)))
       (pack-plt plt-output
diff --git a/collects/compiler/zo-marshal.rkt b/collects/compiler/zo-marshal.rkt
index 5629f4a917..659d5da608 100644
--- a/collects/compiler/zo-marshal.rkt
+++ b/collects/compiler/zo-marshal.rkt
@@ -127,6 +127,8 @@
   (write-bytes (bytes (bytes-length version-bs)) outp)
   (write-bytes version-bs outp)
 
+  ; Write empty hash code
+  (write-bytes (make-bytes 20 0) outp)
   
   ; Write the symbol table information (size, offsets)
   (define symtabsize (add1 (vector-length symbol-table)))
diff --git a/collects/compiler/zo-parse.rkt b/collects/compiler/zo-parse.rkt
index a4e11f586b..d14a296e28 100644
--- a/collects/compiler/zo-parse.rkt
+++ b/collects/compiler/zo-parse.rkt
@@ -1011,6 +1011,9 @@
       (error 'zo-parse "not a bytecode stream"))
     
     (define version (read-bytes (min 63 (read-byte port)) port))
+
+    ;; Skip module hash code
+    (read-bytes 20 port)
     
     (define symtabsize (read-simple-number port))