Index: src/vdbemem.c
==================================================================
--- src/vdbemem.c
+++ src/vdbemem.c
@@ -160,11 +160,14 @@
     return SQLITE_OK;   /* Nothing to do */
   }
   if( pMem->flags & (MEM_Static|MEM_Ephem) ){
     return sqlite3VdbeMemMakeWriteable(pMem);
   }else{
-    char *z = sqliteMalloc(pMem->n+2);
+    char *z; 
+    sqlite3VdbeMemExpandBlob(pMem);
+    z = sqliteMalloc(pMem->n+2);
+
     if( !z ) return SQLITE_NOMEM;
     memcpy(z, pMem->z, pMem->n);
     z[pMem->n] = 0;
     z[pMem->n+1] = 0;
     if( pMem->xDel ){

Index: test/zeroblob.test
==================================================================
--- test/zeroblob.test
+++ test/zeroblob.test
@@ -11,11 +11,11 @@
 # This file implements regression tests for SQLite library.  The
 # focus of this file is testing of the zero-filled blob functionality
 # including the sqlite3_bind_zeroblob(), sqlite3_result_zeroblob(),
 # and the built-in zeroblob() SQL function.
 #
-# $Id: zeroblob.test,v 1.4 2007/05/23 06:31:39 drh Exp $
+# $Id: zeroblob.test,v 1.5 2007/05/30 06:19:33 danielk1977 Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
 
 ifcapable !incrblob {
@@ -125,8 +125,31 @@
 do_test zeroblob-4.1 {
   execsql {
     SELECT hex(zeroblob(2) || x'61')
   }
 } {000061}
+
+# Check various CAST(...) operations on zeroblob.
+#
+do_test zeroblob-5.1 {
+  execsql {
+    SELECT CAST (zeroblob(100) AS REAL);
+  }
+} {0.0}
+do_test zeroblob-5.2 {
+  execsql {
+    SELECT CAST (zeroblob(100) AS INTEGER);
+  }
+} {0}
+do_test zeroblob-5.3 {
+  execsql {
+    SELECT CAST (zeroblob(100) AS TEXT);
+  }
+} {{}}
+do_test zeroblob-5.4 {
+  execsql {
+    SELECT CAST(zeroblob(100) AS BLOB);
+  }
+} [execsql {SELECT zeroblob(100)}]
   
 
 finish_test