Index: src/whereexpr.c
==================================================================
--- src/whereexpr.c
+++ src/whereexpr.c
@@ -1380,10 +1380,11 @@
   ** Note that the virtual term must be tagged with TERM_VNULL.
   */
   if( pExpr->op==TK_NOTNULL
    && pExpr->pLeft->op==TK_COLUMN
    && pExpr->pLeft->iColumn>=0
+   && !ExprHasProperty(pExpr, EP_FromJoin)
    && OptimizationEnabled(db, SQLITE_Stat34)
   ){
     Expr *pNewExpr;
     Expr *pLeft = pExpr->pLeft;
     int idxNew;

Index: test/where.test
==================================================================
--- test/where.test
+++ test/where.test
@@ -1410,7 +1410,20 @@
   AND (b=1 OR c=1);
 } {
   4 1 0
   4 0 1
 }
+
+# 2018-11-05: ticket [https://www.sqlite.org/src/tktview/65eb38f6e46de8c75e188a]
+# Incorrect result in LEFT JOIN when STAT4 is enabled.
+#
+sqlite3 db :memory:
+do_execsql_test where-22.1 {
+  CREATE TABLE t1(a INT);
+  CREATE INDEX t1a ON t1(a);
+  INSERT INTO t1(a) VALUES(NULL),(NULL),(42),(NULL),(NULL);
+  CREATE TABLE t2(dummy INT);
+  SELECT count(*) FROM t1 LEFT JOIN t2 ON a IS NOT NULL;
+} {5}
+
 
 finish_test