Index: src/resolve.c
==================================================================
--- src/resolve.c
+++ src/resolve.c
@@ -432,10 +432,14 @@
           assert( pExpr->x.pSelect==0 );
           pOrig = pEList->a[j].pExpr;
           if( (pNC->ncFlags&NC_AllowAgg)==0 && ExprHasProperty(pOrig, EP_Agg) ){
             sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
             return WRC_Abort;
+          }
+          if( (pNC->ncFlags&NC_AllowWin)==0 && ExprHasProperty(pOrig, EP_Win) ){
+            sqlite3ErrorMsg(pParse, "misuse of aliased window function %s",zAs);
+            return WRC_Abort;
           }
           if( sqlite3ExprVectorSize(pOrig)!=1 ){
             sqlite3ErrorMsg(pParse, "row value misused");
             return WRC_Abort;
           }
@@ -723,10 +727,11 @@
       int is_agg = 0;             /* True if is an aggregate function */
       int nId;                    /* Number of characters in function name */
       const char *zId;            /* The function name. */
       FuncDef *pDef;              /* Information about the function */
       u8 enc = ENC(pParse->db);   /* The database encoding */
+      int savedAllowFlags = (pNC->ncFlags & (NC_AllowAgg | NC_AllowWin));
 
       assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
       zId = pExpr->u.zToken;
       nId = sqlite3Strlen30(zId);
       pDef = sqlite3FindFunction(pParse->db, zId, n, enc, 0);
@@ -844,12 +849,15 @@
           sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",
                nId, zId);
           pNC->nErr++;
         }
         if( is_agg ){
+          /* Window functions may not be arguments of aggregate functions.
+          ** Or arguments of other window functions. But aggregate functions
+          ** may be arguments for window functions.  */
 #ifndef SQLITE_OMIT_WINDOWFUNC
-          pNC->ncFlags &= ~(pExpr->y.pWin ? NC_AllowWin : NC_AllowAgg);
+          pNC->ncFlags &= ~(NC_AllowWin | (!pExpr->y.pWin ? NC_AllowAgg : 0));
 #else
           pNC->ncFlags &= ~NC_AllowAgg;
 #endif
         }
       }
@@ -866,11 +874,11 @@
            || 0==sqlite3WindowCompare(pParse, pSel->pWin, pExpr->y.pWin) 
           ){
             pExpr->y.pWin->pNextWin = pSel->pWin;
             pSel->pWin = pExpr->y.pWin;
           }
-          pNC->ncFlags |= NC_AllowWin;
+          pNC->ncFlags |= NC_HasWin;
         }else
 #endif /* SQLITE_OMIT_WINDOWFUNC */
         {
           NameContext *pNC2 = pNC;
           pExpr->op = TK_AGG_FUNCTION;
@@ -884,12 +892,12 @@
             assert( SQLITE_FUNC_MINMAX==NC_MinMaxAgg );
             testcase( (pDef->funcFlags & SQLITE_FUNC_MINMAX)!=0 );
             pNC2->ncFlags |= NC_HasAgg | (pDef->funcFlags & SQLITE_FUNC_MINMAX);
 
           }
-          pNC->ncFlags |= NC_AllowAgg;
         }
+        pNC->ncFlags |= savedAllowFlags;
       }
       /* FIX ME:  Compute pExpr->affinity based on the expected return
       ** type of the function 
       */
       return WRC_Prune;
@@ -1646,12 +1654,12 @@
 ){
   u16 savedHasAgg;
   Walker w;
 
   if( pExpr==0 ) return SQLITE_OK;
-  savedHasAgg = pNC->ncFlags & (NC_HasAgg|NC_MinMaxAgg);
-  pNC->ncFlags &= ~(NC_HasAgg|NC_MinMaxAgg);
+  savedHasAgg = pNC->ncFlags & (NC_HasAgg|NC_MinMaxAgg|NC_HasWin);
+  pNC->ncFlags &= ~(NC_HasAgg|NC_MinMaxAgg|NC_HasWin);
   w.pParse = pNC->pParse;
   w.xExprCallback = resolveExprStep;
   w.xSelectCallback = resolveSelectStep;
   w.xSelectCallback2 = 0;
   w.u.pNC = pNC;
@@ -1666,10 +1674,13 @@
   w.pParse->nHeight -= pExpr->nHeight;
 #endif
   if( pNC->ncFlags & NC_HasAgg ){
     ExprSetProperty(pExpr, EP_Agg);
   }
+  if( pNC->ncFlags & NC_HasWin ){
+    ExprSetProperty(pExpr, EP_Win);
+  }
   pNC->ncFlags |= savedHasAgg;
   return pNC->nErr>0 || w.pParse->nErr>0;
 }
 
 /*

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -2522,10 +2522,11 @@
 #define EP_Alias     0x400000 /* Is an alias for a result set column */
 #define EP_Leaf      0x800000 /* Expr.pLeft, .pRight, .u.pSelect all NULL */
 #define EP_WinFunc  0x1000000 /* TK_FUNCTION with Expr.y.pWin set */
 #define EP_Subrtn   0x2000000 /* Uses Expr.y.sub. TK_IN, _SELECT, or _EXISTS */
 #define EP_Quoted   0x4000000 /* TK_ID was originally quoted */
+#define EP_Win      0x8000000 /* Contains window functions */
 
 /*
 ** The EP_Propagate mask is a set of properties that automatically propagate
 ** upwards into parent nodes.
 */
@@ -2778,10 +2779,11 @@
 #define NC_UAggInfo  0x0100  /* True if uNC.pAggInfo is used */
 #define NC_UUpsert   0x0200  /* True if uNC.pUpsert is used */
 #define NC_MinMaxAgg 0x1000  /* min/max aggregates seen.  See note above */
 #define NC_Complex   0x2000  /* True if a function or subquery seen */
 #define NC_AllowWin  0x4000  /* Window functions are allowed here */
+#define NC_HasWin    0x8000  /* One or more window functions seen */
 
 /*
 ** An instance of the following object describes a single ON CONFLICT
 ** clause in an upsert.
 **

Index: test/windowerr.tcl
==================================================================
--- test/windowerr.tcl
+++ test/windowerr.tcl
@@ -45,8 +45,16 @@
   SELECT a, sum(b) OVER (
     $frame
   ) FROM t1 ORDER BY 1
   "
 }
+errorsql_test 2.1 {
+  SELECT sum( sum(a) OVER () ) FROM t1;
+}
+
+errorsql_test 2.2 {
+  SELECT sum(a) OVER () AS xyz FROM t1 ORDER BY sum(xyz);
+}
+
 
 finish_test
 

Index: test/windowerr.test
==================================================================
--- test/windowerr.test
+++ test/windowerr.test
@@ -83,7 +83,17 @@
 do_test 1.8 { catch { execsql {
   SELECT a, sum(b) OVER (
     PARTITION BY a RANGE BETWEEN  1 PRECEDING AND 1 FOLLOWING
   ) FROM t1 ORDER BY 1
 } } } 1
+
+# PG says ERROR:  aggregate function calls cannot contain window function calls
+do_test 2.1 { catch { execsql {
+  SELECT sum( sum(a) OVER () ) FROM t1;
+} } } 1
+
+# PG says ERROR:  column "xyz" does not exist
+do_test 2.2 { catch { execsql {
+  SELECT sum(a) OVER () AS xyz FROM t1 ORDER BY sum(xyz);
+} } } 1
 
 finish_test