Index: src/where.c
==================================================================
--- src/where.c
+++ src/where.c
@@ -2449,11 +2449,10 @@
         || (pNew->wsFlags & WHERE_SKIPSCAN)!=0 
     );
 
     if( eOp & WO_IN ){
       Expr *pExpr = pTerm->pExpr;
-      LogEst M, logK;
       if( ExprHasProperty(pExpr, EP_xIsSelect) ){
         /* "x IN (SELECT ...)":  TUNING: the SELECT returns 25 rows */
         int i;
         nIn = 46;  assert( 46==sqlite3LogEst(25) );
 
@@ -2470,10 +2469,11 @@
         nIn = sqlite3LogEst(pExpr->x.pList->nExpr);
         assert( nIn>0 );  /* RHS always has 2 or more terms...  The parser
                           ** changes "x IN (?)" into "x=?". */
       }
       if( pProbe->hasStat1 ){
+        LogEst M, logK, safetyMargin;
         /* Let:
         **   N = the total number of rows in the table
         **   K = the number of entries on the RHS of the IN operator
         **   M = the number of rows in the table that match terms to the 
         **       to the left in the same index.  If the IN operator is on
@@ -2491,11 +2491,12 @@
         ** If we do not have real sqlite_stat1 data, always prefer to use
         ** the index.
         */
         M = pProbe->aiRowLogEst[saved_nEq];
         logK = estLog(nIn);
-        if( M + logK + 10 < nIn + rLogSize ){
+        safetyMargin = 10;  /* TUNING: extra weight for indexed IN */
+        if( M + logK + safetyMargin < nIn + rLogSize ){
           WHERETRACE(0x40,
             ("Scan preferred over IN operator on column %d of \"%s\" (%d<%d)\n",
              saved_nEq, pProbe->zName, M+logK+10, nIn+rLogSize));
           continue;
         }else{