Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -1779,18 +1779,22 @@
 int sqlite3_ckpt_open(
   sqlite3 *db, 
   unsigned char *a, int n, 
   sqlite3_ckpt **ppCkpt
 ){
-  Pager *pPager;
-  Btree *pBt;
+  Pager *pPager = 0;
   int rc;
 
   *ppCkpt = 0;
   sqlite3_mutex_enter(db->mutex);
-  pBt = db->aDb[0].pBt;
-  pPager = sqlite3BtreePager(pBt);
+
+  /* Find the Pager object. */
+  rc = sqlite3_file_control(db,"main",SQLITE_FCNTL_ZIPVFS_PAGER,(void*)&pPager);
+  if( rc!=SQLITE_OK ){
+    pPager = sqlite3BtreePager(db->aDb[0].pBt);
+  }
+
   rc = sqlite3PagerWalCheckpointStart(db, pPager, a, n, ppCkpt);
   sqlite3_mutex_leave(db->mutex);
   return rc;
 }
 

Index: src/sqlite.h.in
==================================================================
--- src/sqlite.h.in
+++ src/sqlite.h.in
@@ -939,10 +939,14 @@
 ** The [SQLITE_FCNTL_WIN32_SET_HANDLE] opcode is used for debugging.  This
 ** opcode causes the xFileControl method to swap the file handle with the one
 ** pointed to by the pArg argument.  This capability is used during testing
 ** and only needs to be supported when SQLITE_TEST is defined.
 **
+** <li>[[SQLITE_FCNTL_ZIPVFS_PAGER]]
+** The [SQLITE_FCNTL_ZIPVFS_PAGER] opcode is used by the OTA extension when
+** updating a zipvfs database.
+**
 ** </ul>
 */
 #define SQLITE_FCNTL_LOCKSTATE               1
 #define SQLITE_GET_LOCKPROXYFILE             2
 #define SQLITE_SET_LOCKPROXYFILE             3
@@ -963,10 +967,11 @@
 #define SQLITE_FCNTL_TRACE                  19
 #define SQLITE_FCNTL_HAS_MOVED              20
 #define SQLITE_FCNTL_SYNC                   21
 #define SQLITE_FCNTL_COMMIT_PHASETWO        22
 #define SQLITE_FCNTL_WIN32_SET_HANDLE       23
+#define SQLITE_FCNTL_ZIPVFS_PAGER           24
 
 /*
 ** CAPI3REF: Mutex Handle
 **
 ** The mutex module within SQLite defines [sqlite3_mutex] to be an