Index: src/pager.c
==================================================================
--- src/pager.c
+++ src/pager.c
@@ -517,17 +517,17 @@
 ** that the database-connection mutex is held for pager X and asserts if it
 ** is not.
 */
 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
   static void pagerEnter(Pager *p){
-    p->iInUseDB++;
-    if( p->iInUseMM && p->iInUseDB==1 ){
+    if( p->iInUseDB>0 ){
+      p->iInUseDB++;
+    }else{
 #ifndef SQLITE_MUTEX_NOOP
       sqlite3_mutex *mutex;
       mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM2);
 #endif
-      p->iInUseDB = 0;
       sqlite3_mutex_enter(mutex);
       assert( p->iInUseMM==0 );
       p->iInUseDB = 1;
       sqlite3_mutex_leave(mutex);
     }
@@ -3316,13 +3316,15 @@
     ** be released.
     */
     if( !pPg ) break;
 
     pPager = pPg->pPager;
+    assert( pPager->iInUseDB==0 );
     savedBusy = pPager->pBusyHandler;
     pPager->pBusyHandler = 0;
     rc = pager_recycle(pPager, &pPg);
+    assert( pPager->iInUseDB==0 );
     pPager->pBusyHandler = savedBusy;
     if( rc==SQLITE_OK ){
       /* We've found a page to free. At this point the page has been 
       ** removed from the page hash-table, free-list and synced-list 
       ** (pFirstSynced). It is still in the all pages (pAll) list.