diff --git a/doc/src/sgml/ref/alter_function.sgml b/doc/src/sgml/ref/alter_function.sgml
index 3ceb6123f4f..013b6f8401c 100644
--- a/doc/src/sgml/ref/alter_function.sgml
+++ b/doc/src/sgml/ref/alter_function.sgml
@@ -33,7 +33,7 @@ ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="paramet
 <phrase>where <replaceable class="PARAMETER">action</replaceable> is one of:</phrase>
 
     CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT
-    IMMUTABLE | STABLE | VOLATILE | LEAKPROOF
+    IMMUTABLE | STABLE | VOLATILE | [ NOT ] LEAKPROOF
     [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
     COST <replaceable class="parameter">execution_cost</replaceable>
     ROWS <replaceable class="parameter">result_rows</replaceable>
diff --git a/doc/src/sgml/ref/create_function.sgml b/doc/src/sgml/ref/create_function.sgml
index 7df66ab0e08..4336e4b2182 100644
--- a/doc/src/sgml/ref/create_function.sgml
+++ b/doc/src/sgml/ref/create_function.sgml
@@ -26,7 +26,7 @@ CREATE [ OR REPLACE ] FUNCTION
       | RETURNS TABLE ( <replaceable class="parameter">column_name</replaceable> <replaceable class="parameter">column_type</replaceable> [, ...] ) ]
   { LANGUAGE <replaceable class="parameter">lang_name</replaceable>
     | WINDOW
-    | IMMUTABLE | STABLE | VOLATILE | LEAKPROOF
+    | IMMUTABLE | STABLE | VOLATILE | [ NOT ] LEAKPROOF
     | CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT
     | [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
     | COST <replaceable class="parameter">execution_cost</replaceable>
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index db63ff23711..d1ce2ab0422 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -370,7 +370,7 @@ static void processCASbits(int cas_bits, int location, const char *constrType,
 
 %type <istmt>	insert_rest
 
-%type <vsetstmt> set_rest SetResetClause
+%type <vsetstmt> set_rest set_rest_more SetResetClause FunctionSetResetClause
 
 %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
 				ForeignTableElement
@@ -1227,7 +1227,27 @@ VariableSetStmt:
 				}
 		;
 
-set_rest:	/* Generic SET syntaxes: */
+set_rest:
+			TRANSACTION transaction_mode_list
+				{
+					VariableSetStmt *n = makeNode(VariableSetStmt);
+					n->kind = VAR_SET_MULTI;
+					n->name = "TRANSACTION";
+					n->args = $2;
+					$$ = n;
+				}
+			| SESSION CHARACTERISTICS AS TRANSACTION transaction_mode_list
+				{
+					VariableSetStmt *n = makeNode(VariableSetStmt);
+					n->kind = VAR_SET_MULTI;
+					n->name = "SESSION CHARACTERISTICS";
+					n->args = $5;
+					$$ = n;
+				}
+			| set_rest_more
+			;
+
+set_rest_more:	/* Generic SET syntaxes: */
 			var_name TO var_list
 				{
 					VariableSetStmt *n = makeNode(VariableSetStmt);
@@ -1277,22 +1297,6 @@ set_rest:	/* Generic SET syntaxes: */
 						n->kind = VAR_SET_DEFAULT;
 					$$ = n;
 				}
-			| TRANSACTION transaction_mode_list
-				{
-					VariableSetStmt *n = makeNode(VariableSetStmt);
-					n->kind = VAR_SET_MULTI;
-					n->name = "TRANSACTION";
-					n->args = $2;
-					$$ = n;
-				}
-			| SESSION CHARACTERISTICS AS TRANSACTION transaction_mode_list
-				{
-					VariableSetStmt *n = makeNode(VariableSetStmt);
-					n->kind = VAR_SET_MULTI;
-					n->name = "SESSION CHARACTERISTICS";
-					n->args = $5;
-					$$ = n;
-				}
 			| CATALOG_P Sconst
 				{
 					ereport(ERROR,
@@ -1512,6 +1516,12 @@ SetResetClause:
 			| VariableResetStmt				{ $$ = (VariableSetStmt *) $1; }
 		;
 
+/* SetResetClause allows SET or RESET without LOCAL */
+FunctionSetResetClause:
+			SET set_rest_more				{ $$ = $2; }
+			| VariableResetStmt				{ $$ = (VariableSetStmt *) $1; }
+		;
+
 
 VariableShowStmt:
 			SHOW var_name
@@ -6119,6 +6129,10 @@ common_func_opt_item:
 				{
 					$$ = makeDefElem("leakproof", (Node *)makeInteger(TRUE));
 				}
+			| NOT LEAKPROOF
+				{
+					$$ = makeDefElem("leakproof", (Node *)makeInteger(FALSE));
+				}
 			| COST NumericOnly
 				{
 					$$ = makeDefElem("cost", (Node *)$2);
@@ -6127,7 +6141,7 @@ common_func_opt_item:
 				{
 					$$ = makeDefElem("rows", (Node *)$2);
 				}
-			| SetResetClause
+			| FunctionSetResetClause
 				{
 					/* we abuse the normal content of a DefElem here */
 					$$ = makeDefElem("set", (Node *)$1);