diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 8f133b0..adf789e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -663,6 +663,11 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * and for NULL so that it can follow b_expr in ColQualList without creating
  * postfix-operator problems.
  *
+ * To support CUBE and ROLLUP in GROUP BY without reserving them, we give them
+ * an explicit priority lower than '(', so that a rule with CUBE '(' will shift
+ * rather than reducing a conflicting rule that takes CUBE as a function name.
+ * Using the same precedence as IDENT seems right for the reasons given above.
+ *
  * The frame_bound productions UNBOUNDED PRECEDING and UNBOUNDED FOLLOWING
  * are even messier: since UNBOUNDED is an unreserved keyword (per spec!),
  * there is no principled way to distinguish these from the productions
@@ -673,7 +678,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * blame any funny behavior of UNBOUNDED on the SQL standard, though.
  */
 %nonassoc	UNBOUNDED		/* ideally should have same precedence as IDENT */
-%nonassoc	IDENT NULL_P PARTITION RANGE ROWS PRECEDING FOLLOWING
+%nonassoc	IDENT NULL_P PARTITION RANGE ROWS PRECEDING FOLLOWING CUBE ROLLUP
 %left		Op OPERATOR		/* multi-character ops and user-defined operators */
 %nonassoc	NOTNULL
 %nonassoc	ISNULL
@@ -9891,6 +9896,12 @@ empty_grouping_set:
 				}
 		;
 
+/*
+ * These hacks rely on setting precedence of CUBE and ROLLUP below that of '(',
+ * so that they shift in these rules rather than reducing the conflicting
+ * unreserved_keyword rule.
+ */
+
 rollup_clause:
 			ROLLUP '(' expr_list ')'
 				{
@@ -13012,6 +13023,7 @@ unreserved_keyword:
 			| COPY
 			| COST
 			| CSV
+			| CUBE
 			| CURRENT_P
 			| CURSOR
 			| CYCLE
@@ -13158,6 +13170,7 @@ unreserved_keyword:
 			| REVOKE
 			| ROLE
 			| ROLLBACK
+			| ROLLUP
 			| ROWS
 			| RULE
 			| SAVEPOINT
@@ -13249,7 +13262,6 @@ col_name_keyword:
 			| CHAR_P
 			| CHARACTER
 			| COALESCE
-			| CUBE
 			| DEC
 			| DECIMAL_P
 			| EXISTS
@@ -13272,7 +13284,6 @@ col_name_keyword:
 			| POSITION
 			| PRECISION
 			| REAL
-			| ROLLUP
 			| ROW
 			| SETOF
 			| SMALLINT
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 5344736..e170964 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4888,12 +4888,13 @@ get_rule_sortgroupclause(Index ref, List *tlist, bool force_colno,
 	expr = (Node *) tle->expr;
 
 	/*
-	 * Use column-number form if requested by caller.  Otherwise, if
-	 * expression is a constant, force it to be dumped with an explicit cast
-	 * as decoration --- this is because a simple integer constant is
-	 * ambiguous (and will be misinterpreted by findTargetlistEntry()) if we
-	 * dump it without any decoration.  Otherwise, just dump the expression
-	 * normally.
+	 * Use column-number form if requested by caller.  Otherwise, if expression
+	 * is a constant, force it to be dumped with an explicit cast as decoration
+	 * --- this is because a simple integer constant is ambiguous (and will be
+	 * misinterpreted by findTargetlistEntry()) if we dump it without any
+	 * decoration.  If it's anything more complex than a simple Var, then force
+	 * extra parens around it, to ensure it can't be misinterpreted as a cube()
+	 * or rollup() construct.
 	 */
 	if (force_colno)
 	{
@@ -4902,8 +4903,27 @@ get_rule_sortgroupclause(Index ref, List *tlist, bool force_colno,
 	}
 	else if (expr && IsA(expr, Const))
 		get_const_expr((Const *) expr, context, 1);
+	else if (!expr || IsA(expr, Var))
+		get_rule_expr(expr, context, true);
 	else
+	{
+		/*
+		 * We must force parens for function-like expressions even if
+		 * PRETTY_PAREN is off, since those are the ones in danger of
+		 * misparsing. For other expressions we need to force them
+		 * only if PRETTY_PAREN is on, since otherwise the expression
+		 * will output them itself. (We can't skip the parens.)
+		 */
+		bool	need_paren = (PRETTY_PAREN(context)
+							  || IsA(expr, FuncExpr)
+							  || IsA(expr, Aggref)
+							  || IsA(expr, WindowFunc));
+		if (need_paren)
+			appendStringInfoString(context->buf, "(");
 		get_rule_expr(expr, context, true);
+		if (need_paren)
+			appendStringInfoString(context->buf, ")");
+	}
 
 	return expr;
 }
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index e38b6bc..5ea1067 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -98,7 +98,7 @@ PG_KEYWORD("cost", COST, UNRESERVED_KEYWORD)
 PG_KEYWORD("create", CREATE, RESERVED_KEYWORD)
 PG_KEYWORD("cross", CROSS, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("csv", CSV, UNRESERVED_KEYWORD)
-PG_KEYWORD("cube", CUBE, COL_NAME_KEYWORD)
+PG_KEYWORD("cube", CUBE, UNRESERVED_KEYWORD)
 PG_KEYWORD("current", CURRENT_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("current_catalog", CURRENT_CATALOG, RESERVED_KEYWORD)
 PG_KEYWORD("current_date", CURRENT_DATE, RESERVED_KEYWORD)
@@ -324,7 +324,7 @@ PG_KEYWORD("revoke", REVOKE, UNRESERVED_KEYWORD)
 PG_KEYWORD("right", RIGHT, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("role", ROLE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rollback", ROLLBACK, UNRESERVED_KEYWORD)
-PG_KEYWORD("rollup", ROLLUP, COL_NAME_KEYWORD)
+PG_KEYWORD("rollup", ROLLUP, UNRESERVED_KEYWORD)
 PG_KEYWORD("row", ROW, COL_NAME_KEYWORD)
 PG_KEYWORD("rows", ROWS, UNRESERVED_KEYWORD)
 PG_KEYWORD("rule", RULE, UNRESERVED_KEYWORD)