Index: src/backup.c
==================================================================
--- src/backup.c
+++ src/backup.c
@@ -683,13 +683,17 @@
 **
 ** It is assumed that the mutex associated with the BtShared object
 ** corresponding to the source database is held when this function is
 ** called.
 */
-void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
-  sqlite3_backup *p;                   /* Iterator variable */
-  for(p=pBackup; p; p=p->pNext){
+static SQLITE_NOINLINE void backupUpdate(
+  sqlite3_backup *p,
+  Pgno iPage,
+  const u8 *aData
+){
+  assert( p!=0 );
+  do{
     assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
     if( !isFatalError(p->rc) && iPage<p->iNext ){
       /* The backup process p has already copied page iPage. But now it
       ** has been modified by a transaction on the source pager. Copy
       ** the new data into the backup.
@@ -702,11 +706,14 @@
       assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
       if( rc!=SQLITE_OK ){
         p->rc = rc;
       }
     }
-  }
+  }while( (p = p->pNext)!=0 );
+}
+void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
+  if( pBackup ) backupUpdate(pBackup, iPage, aData);
 }
 
 /*
 ** Restart the backup process. This is called when the pager layer
 ** detects that the database has been modified by an external database