Index: src/pager.c
==================================================================
--- src/pager.c
+++ src/pager.c
@@ -5374,11 +5374,15 @@
   assert( pPager->hasHeldSharedLock==1 );
 
   pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
   if( pBase==0 ){
     pPg = 0;
-    rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
+    if( pgno==0 ){
+      rc = SQLITE_CORRUPT_BKPT;
+    }else{
+      rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
+    }
     if( rc!=SQLITE_OK ) goto pager_acquire_err;
     if( pBase==0 ){
       rc = SQLITE_NOMEM_BKPT;
       goto pager_acquire_err;
     }
@@ -5398,15 +5402,15 @@
 
   }else{
     /* The pager cache has created a new page. Its content needs to 
     ** be initialized. But first some error checks:
     **
-    ** (1) Minimum page number is 1
-    ** (2) The maximum page number is 2^31
-    ** (3) Never try to fetch the locking page
+    ** (1) The maximum page number is 2^31
+    ** (2) Never try to fetch the locking page
     */
-    if( pgno==0 || pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
+    assert( pgno>0 );
+    if( pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
       rc = SQLITE_CORRUPT_BKPT;
       goto pager_acquire_err;
     }
 
     pPg->pPager = pPager;

Index: src/pcache1.c
==================================================================
--- src/pcache1.c
+++ src/pcache1.c
@@ -995,11 +995,11 @@
     if( !pPage->isPinned ){
       return pcache1PinPage(pPage);
     }else{
       return pPage;
     }
-  }else if( createFlag ){
+  }else if( createFlag && iKey ){
     /* Steps 3, 4, and 5 implemented by this subroutine */
     return pcache1FetchStage2(pCache, iKey, createFlag);
   }else{
     return 0;
   }

Index: src/sqlite.h.in
==================================================================
--- src/sqlite.h.in
+++ src/sqlite.h.in
@@ -7213,11 +7213,12 @@
 ** single database page.  The pExtra element of sqlite3_pcache_page will be
 ** a pointer to the szExtra bytes of extra storage that SQLite has requested
 ** for each entry in the page cache.
 **
 ** The page to be fetched is determined by the key. ^The minimum key value
-** is 1.  After it has been retrieved using xFetch, the page is considered
+** is 1.  The xFetch() method must return NULL if passed a key of 0.
+** After it has been retrieved using xFetch, the page is considered
 ** to be "pinned".
 **
 ** If the requested page is already in the page cache, then the page cache
 ** implementation must return a pointer to the page buffer with its content
 ** intact.  If the requested page is not already in the cache, then the
@@ -7225,14 +7226,15 @@
 ** parameter to help it determined what action to take:
 **
 ** <table border=1 width=85% align=center>
 ** <tr><th> createFlag <th> Behavior when page is not already in cache
 ** <tr><td> 0 <td> Do not allocate a new page.  Return NULL.
-** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so.
-**                 Otherwise return NULL.
+** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so
+**                 and the key is not zero.  Otherwise return NULL.
 ** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
-**                 NULL if allocating a new page is effectively impossible.
+**                 NULL if the key is zero or if allocating a new page is 
+**                 effectively impossible.
 ** </table>
 **
 ** ^(SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  SQLite
 ** will only use a createFlag of 2 after a prior call with a createFlag of 1
 ** failed.)^  In between the to xFetch() calls, SQLite may