Index: src/parse.y
==================================================================
--- src/parse.y
+++ src/parse.y
@@ -1740,10 +1740,12 @@
 filter_over(A) ::= filter_clause(F). {
   A = (Window*)sqlite3DbMallocZero(pParse->db, sizeof(Window));
   if( A ){
     A->eFrmType = TK_FILTER;
     A->pFilter = F;
+  }else{
+    sqlite3ExprDelete(pParse->db, F);
   }
 }
 
 over_clause(A) ::= OVER LP window(Z) RP. {
   A = Z;

ADDED   test/filterfault.test
Index: test/filterfault.test
==================================================================
--- test/filterfault.test
+++ test/filterfault.test
@@ -0,0 +1,44 @@
+# 2018 May 8
+#
+# 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.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix filterfault
+
+ifcapable !windowfunc {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(a, b, c, d);
+  INSERT INTO t1 VALUES(1, 2, 3, 4);
+  INSERT INTO t1 VALUES(5, 6, 7, 8);
+  INSERT INTO t1 VALUES(9, 10, 11, 12);
+}
+faultsim_save_and_close
+
+do_faultsim_test 1 -faults oom-t* -prep {
+  faultsim_restore_and_reopen
+} -body {
+  execsql {
+    SELECT sum(a) FILTER (WHERE b<5),
+           count() FILTER (WHERE d!=c) 
+      FROM t1 GROUP BY c ORDER BY 1;
+  }
+} -test {
+  faultsim_test_result {0 {{} 1 {} 1 1 1}}
+}
+
+
+finish_test