Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -3692,19 +3692,17 @@
   pFree = 0;  /* Not needed.  Only used to suppress a compiler warning. */
   if( pOp->p4.i>0 ){
     r.pKeyInfo = pC->pKeyInfo;
     r.nField = (u16)pOp->p4.i;
     r.aMem = pIn3;
+    for(ii=0; ii<r.nField; ii++){
+      assert( memIsValid(&r.aMem[ii]) );
+      ExpandBlob(&r.aMem[ii]);
 #ifdef SQLITE_DEBUG
-    {
-      int i;
-      for(i=0; i<r.nField; i++){
-        assert( memIsValid(&r.aMem[i]) );
-        if( i ) REGISTER_TRACE(pOp->p3+i, &r.aMem[i]);
-      }
+      if( ii ) REGISTER_TRACE(pOp->p3+ii, &r.aMem[ii]);
+#endif
     }
-#endif
     r.flags = UNPACKED_PREFIX_MATCH;
     pIdxKey = &r;
   }else{
     pIdxKey = sqlite3VdbeAllocUnpackedRecord(
         pC->pKeyInfo, aTempRec, sizeof(aTempRec), &pFree

Index: test/distinct.test
==================================================================
--- test/distinct.test
+++ test/distinct.test
@@ -194,7 +194,32 @@
 do_test 3.1 {
   regexp {OpenEphemeral} [db eval {
     EXPLAIN SELECT DISTINCT a, b FROM t3 ORDER BY +a, +b;
   }]
 } {0}
+
+#-------------------------------------------------------------------------
+# Ticket  [fccbde530a6583bf2748400919f1603d5425995c] (2014-01-08)
+# The logic that computes DISTINCT sometimes thinks that a zeroblob()
+# and a blob of all zeros are different when they should be the same. 
+#
+do_execsql_test 4.1 {
+  DROP TABLE IF EXISTS t1;
+  DROP TABLE IF EXISTS t2;
+  CREATE TABLE t1(a INTEGER);
+  INSERT INTO t1 VALUES(3);
+  INSERT INTO t1 VALUES(2);
+  INSERT INTO t1 VALUES(1);
+  INSERT INTO t1 VALUES(2);
+  INSERT INTO t1 VALUES(3);
+  INSERT INTO t1 VALUES(1);
+  CREATE TABLE t2(x);
+  INSERT INTO t2
+    SELECT DISTINCT
+      CASE a WHEN 1 THEN x'0000000000'
+             WHEN 2 THEN zeroblob(5)
+             ELSE 'xyzzy' END
+      FROM t1;
+  SELECT quote(x) FROM t2 ORDER BY 1;
+} {'xyzzy' X'0000000000'}
 
 finish_test