Index: src/btree.c
==================================================================
--- src/btree.c
+++ src/btree.c
@@ -4805,10 +4805,14 @@
         }
         if( k==0 ){
           if( !pPrevTrunk ){
             memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
           }else{
+            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
+            if( rc!=SQLITE_OK ){
+              goto end_allocate_page;
+            }
             memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
           }
         }else{
           /* The trunk page is required by the caller but it contains 
           ** pointers to free-list leaves. The first leaf becomes a trunk

ADDED   test/tkt-5e10420e8d.test
Index: test/tkt-5e10420e8d.test
==================================================================
--- /dev/null
+++ test/tkt-5e10420e8d.test
@@ -0,0 +1,50 @@
+# 2010 August 23
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+
+do_execsql_test tkt-5e10420e8d.1 {
+  PRAGMA page_size = 1024;
+  PRAGMA auto_vacuum = incremental;
+
+  CREATE TABLE t1(x);
+  CREATE TABLE t2(x);
+  CREATE TABLE t3(x);
+} {}
+
+do_execsql_test tkt-5e10420e8d.2 {
+  INSERT INTO t3 VALUES(randomblob(500 + 1024*248));
+  INSERT INTO t1 VALUES(randomblob(1500));
+  INSERT INTO t2 VALUES(randomblob(500 + 1024*248));
+
+  DELETE FROM t3;
+  DELETE FROM t2;
+  DELETE FROM t1;
+} {}
+
+do_execsql_test tkt-5e10420e8d.3 {
+  PRAGMA incremental_vacuum(248)
+} {}
+
+do_execsql_test tkt-5e10420e8d.4 {
+  PRAGMA incremental_vacuum(1)
+} {}
+
+db close
+sqlite3 db test.db
+
+do_execsql_test tkt-5e10420e8d.5 {
+  PRAGMA integrity_check;
+} {ok}
+
+finish_test