diff -r eeb2d50ec71f -r ed58e740a699 src/Pure/PIDE/document.ML
--- a/src/Pure/PIDE/document.ML	Thu Jul 24 10:22:34 2014 +0200
+++ b/src/Pure/PIDE/document.ML	Thu Jul 24 10:38:46 2014 +0200
@@ -296,12 +296,7 @@
 
 fun define_blob digest text =
   map_state (fn (versions, blobs, commands, execution) =>
-    let
-      val sha1_digest = SHA1.digest text;
-      val _ =
-        digest = SHA1.rep sha1_digest orelse
-          error ("Ill-defined blob: bad SHA1 digest " ^ digest ^ " vs. " ^ SHA1.rep sha1_digest);
-      val blobs' = Symtab.update (digest, (sha1_digest, split_lines text)) blobs;
+    let val blobs' = Symtab.update (digest, (SHA1.fake digest, split_lines text)) blobs
     in (versions, blobs', commands, execution) end);
 
 fun the_blob (State {blobs, ...}) digest =