diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c98c27a16d..0de9584e53 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -1552,27 +1552,11 @@ zone_value:
 					t->typmods = $3;
 					$$ = makeStringConstCast($2, @2, t);
 				}
-			| ConstInterval '(' Iconst ')' Sconst opt_interval
+			| ConstInterval '(' Iconst ')' Sconst
 				{
 					TypeName *t = $1;
-					if ($6 != NIL)
-					{
-						A_Const *n = (A_Const *) linitial($6);
-						if ((n->val.val.ival & ~(INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE))) != 0)
-							ereport(ERROR,
-									(errcode(ERRCODE_SYNTAX_ERROR),
-									 errmsg("time zone interval must be HOUR or HOUR TO MINUTE"),
-									 parser_errposition(@6)));
-						if (list_length($6) != 1)
-							ereport(ERROR,
-									(errcode(ERRCODE_SYNTAX_ERROR),
-									 errmsg("interval precision specified twice"),
-									 parser_errposition(@1)));
-						t->typmods = lappend($6, makeIntConst($3, @3));
-					}
-					else
-						t->typmods = list_make2(makeIntConst(INTERVAL_FULL_RANGE, -1),
-												makeIntConst($3, @3));
+					t->typmods = list_make2(makeIntConst(INTERVAL_FULL_RANGE, -1),
+											makeIntConst($3, @3));
 					$$ = makeStringConstCast($5, @5, t);
 				}
 			| NumericOnly							{ $$ = makeAConst($1, @1); }
@@ -10582,21 +10566,11 @@ SimpleTypename:
 					$$ = $1;
 					$$->typmods = $2;
 				}
-			| ConstInterval '(' Iconst ')' opt_interval
+			| ConstInterval '(' Iconst ')'
 				{
 					$$ = $1;
-					if ($5 != NIL)
-					{
-						if (list_length($5) != 1)
-							ereport(ERROR,
-									(errcode(ERRCODE_SYNTAX_ERROR),
-									 errmsg("interval precision specified twice"),
-									 parser_errposition(@1)));
-						$$->typmods = lappend($5, makeIntConst($3, @3));
-					}
-					else
-						$$->typmods = list_make2(makeIntConst(INTERVAL_FULL_RANGE, -1),
-												 makeIntConst($3, @3));
+					$$->typmods = list_make2(makeIntConst(INTERVAL_FULL_RANGE, -1),
+											 makeIntConst($3, @3));
 				}
 		;
 
@@ -12923,21 +12897,11 @@ AexprConst: Iconst
 					t->typmods = $3;
 					$$ = makeStringConstCast($2, @2, t);
 				}
-			| ConstInterval '(' Iconst ')' Sconst opt_interval
+			| ConstInterval '(' Iconst ')' Sconst
 				{
 					TypeName *t = $1;
-					if ($6 != NIL)
-					{
-						if (list_length($6) != 1)
-							ereport(ERROR,
-									(errcode(ERRCODE_SYNTAX_ERROR),
-									 errmsg("interval precision specified twice"),
-									 parser_errposition(@1)));
-						t->typmods = lappend($6, makeIntConst($3, @3));
-					}
-					else
-						t->typmods = list_make2(makeIntConst(INTERVAL_FULL_RANGE, -1),
-												makeIntConst($3, @3));
+					t->typmods = list_make2(makeIntConst(INTERVAL_FULL_RANGE, -1),
+											makeIntConst($3, @3));
 					$$ = makeStringConstCast($5, @5, t);
 				}
 			| TRUE_P
diff --git a/src/test/regress/expected/interval.out b/src/test/regress/expected/interval.out
index cf20506bc1..c873a99bd9 100644
--- a/src/test/regress/expected/interval.out
+++ b/src/test/regress/expected/interval.out
@@ -616,16 +616,6 @@ SELECT interval '12:34.5678' minute to second(2);  -- per SQL spec
  00:12:34.57
 (1 row)
 
-SELECT interval(2) '12:34.5678' minute to second;  -- historical PG
-  interval   
--------------
- 00:12:34.57
-(1 row)
-
-SELECT interval(2) '12:34.5678' minute to second(2);  -- syntax error
-ERROR:  interval precision specified twice
-LINE 1: SELECT interval(2) '12:34.5678' minute to second(2);
-               ^
 SELECT interval '1.234' second;
    interval   
 --------------
diff --git a/src/test/regress/sql/interval.sql b/src/test/regress/sql/interval.sql
index 2318917470..789c3de440 100644
--- a/src/test/regress/sql/interval.sql
+++ b/src/test/regress/sql/interval.sql
@@ -183,8 +183,6 @@ SELECT interval '123 2:03 -2:04'; -- not ok, redundant hh:mm fields
 SELECT interval(0) '1 day 01:23:45.6789';
 SELECT interval(2) '1 day 01:23:45.6789';
 SELECT interval '12:34.5678' minute to second(2);  -- per SQL spec
-SELECT interval(2) '12:34.5678' minute to second;  -- historical PG
-SELECT interval(2) '12:34.5678' minute to second(2);  -- syntax error
 SELECT interval '1.234' second;
 SELECT interval '1.234' second(2);
 SELECT interval '1 2.345' day to second(2);