@@ -54,6 +54,8 @@
 # error "FTS5_MAX_PREFIX_INDEXES is too large"
 #endif
 
+#define FTS5_MAX_LEVEL 64
+
 /*
 ** Details:
 **
@@ -4766,10 +4768,10 @@ static Fts5Structure *fts5IndexOptimizeStruct(
   if( pNew ){
     Fts5StructureLevel *pLvl;
     nByte = nSeg * sizeof(Fts5StructureSegment);
-    pNew->nLevel = pStruct->nLevel+1;
+    pNew->nLevel = MIN(pStruct->nLevel+1, FTS5_MAX_LEVEL);
     pNew->nRef = 1;
     pNew->nWriteCounter = pStruct->nWriteCounter;
-    pLvl = &pNew->aLevel[pStruct->nLevel];
+    pLvl = &pNew->aLevel[pNew->nLevel-1];
     pLvl->aSeg = (Fts5StructureSegment*)sqlite3Fts5MallocZero(&p->rc, nByte);
     if( pLvl->aSeg ){
       int iLvl, iSeg;
 
@@ -0,0 +1,64 @@
+# 2014 Dec 20
+#
+# 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.
+#
+#***********************************************************************
+#
+# TESTRUNNER: slow
+#
+
+source [file join [file dirname [info script]] fts5_common.tcl]
+set testprefix fts5optimize2
+
+# If SQLITE_ENABLE_FTS5 is defined, omit this file.
+ifcapable !fts5 {
+  finish_test
+  return
+}
+
+set nLoop 2500
+
+do_execsql_test 1.0 {
+  CREATE VIRTUAL TABLE t1 USING fts5(x);
+  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
+}
+
+do_test 1.1 {
+  for {set ii 0} {$ii < $nLoop} {incr ii} {
+    execsql {
+      INSERT INTO t1 VALUES('abc def ghi');
+      INSERT INTO t1 VALUES('jkl mno pqr');
+      INSERT INTO t1(t1) VALUES('optimize');
+    }
+  }
+} {}
+
+do_execsql_test 1.2 {
+  SELECT count(*) FROM t1('mno')
+} $nLoop
+
+do_execsql_test 2.0 {
+  CREATE VIRTUAL TABLE t2 USING fts5(x);
+  INSERT INTO t2(t2, rank) VALUES('pgsz', 32);
+}
+
+do_test 2.1 {
+  for {set ii 0} {$ii < $nLoop} {incr ii} {
+    execsql {
+      INSERT INTO t2 VALUES('abc def ghi');
+      INSERT INTO t2 VALUES('jkl mno pqr');
+      INSERT INTO t2(t2, rank) VALUES('merge', -1);
+    }
+  }
+} {}
+
+do_execsql_test 2.2 {
+  SELECT count(*) FROM t2('mno')
+} $nLoop
+
+finish_test