Index: src/whereexpr.c
==================================================================
--- src/whereexpr.c
+++ src/whereexpr.c
@@ -911,10 +911,11 @@
   int noCase = 0;                  /* uppercase equivalent to lowercase */
   int op;                          /* Top-level operator.  pExpr->op */
   Parse *pParse = pWInfo->pParse;  /* Parsing context */
   sqlite3 *db = pParse->db;        /* Database connection */
   unsigned char eOp2;              /* op2 value for LIKE/REGEXP/GLOB */
+  int nLeft;                       /* Number of elements on left side vector */
 
   if( db->mallocFailed ){
     return;
   }
   pTerm = &pWC->a[idxTerm];
@@ -1182,17 +1183,16 @@
   **
   ** This is only required if at least one side of the comparison operation
   ** is not a sub-select.  */
   if( pWC->op==TK_AND 
   && (pExpr->op==TK_EQ || pExpr->op==TK_IS)
-  && sqlite3ExprIsVector(pExpr->pLeft)
+  && (nLeft = sqlite3ExprVectorSize(pExpr->pLeft))>1
+  && sqlite3ExprVectorSize(pExpr->pRight)==nLeft
   && ( (pExpr->pLeft->flags & EP_xIsSelect)==0 
-    || (pExpr->pRight->flags & EP_xIsSelect)==0
-  )){
-    int nLeft = sqlite3ExprVectorSize(pExpr->pLeft);
+    || (pExpr->pRight->flags & EP_xIsSelect)==0)
+  ){
     int i;
-    assert( nLeft==sqlite3ExprVectorSize(pExpr->pRight) );
     for(i=0; i<nLeft; i++){
       int idxNew;
       Expr *pNew;
       Expr *pLeft = sqlite3ExprForVectorField(pParse, pExpr->pLeft, i);
       Expr *pRight = sqlite3ExprForVectorField(pParse, pExpr->pRight, i);