diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 417cecff8e..5233a338e6 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.243 2007/04/30 00:14:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.244 2007/05/01 18:53:51 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -3063,11 +3063,11 @@ inline_function(Oid funcid, Oid result_type, List *args,
 	 * compatible with the original expression result type.  To avoid
 	 * confusing matters, insert a RelabelType in such cases.
 	 */
-	if (exprType(newexpr) != funcform->prorettype)
+	if (exprType(newexpr) != result_type)
 	{
-		Assert(IsBinaryCoercible(exprType(newexpr), funcform->prorettype));
+		Assert(IsBinaryCoercible(exprType(newexpr), result_type));
 		newexpr = (Node *) makeRelabelType((Expr *) newexpr,
-										   funcform->prorettype,
+										   result_type,
 										   -1,
 										   COERCE_IMPLICIT_CAST);
 	}
diff --git a/src/test/regress/expected/polymorphism.out b/src/test/regress/expected/polymorphism.out
index 29a0a190d6..de393a0528 100644
--- a/src/test/regress/expected/polymorphism.out
+++ b/src/test/regress/expected/polymorphism.out
@@ -542,3 +542,38 @@ select mysum2(f1, f1 + 1) from t;
      38
 (1 row)
 
+-- test inlining of polymorphic SQL functions
+create function bleat(int) returns int as $$
+begin
+  raise notice 'bleat %', $1;
+  return $1;
+end$$ language plpgsql;
+create function sql_if(bool, anyelement, anyelement) returns anyelement as $$
+select case when $1 then $2 else $3 end $$ language sql;
+-- Note this would fail with integer overflow, never mind wrong bleat() output,
+-- if the CASE expression were not successfully inlined
+select f1, sql_if(f1 > 0, bleat(f1), bleat(f1 + 1)) from int4_tbl;
+NOTICE:  bleat 1
+NOTICE:  bleat 123456
+NOTICE:  bleat -123455
+NOTICE:  bleat 2147483647
+NOTICE:  bleat -2147483646
+     f1      |   sql_if    
+-------------+-------------
+           0 |           1
+      123456 |      123456
+     -123456 |     -123455
+  2147483647 |  2147483647
+ -2147483647 | -2147483646
+(5 rows)
+
+select q2, sql_if(q2 > 0, q2, q2 + 1) from int8_tbl;
+        q2         |      sql_if       
+-------------------+-------------------
+               456 |               456
+  4567890123456789 |  4567890123456789
+               123 |               123
+  4567890123456789 |  4567890123456789
+ -4567890123456789 | -4567890123456788
+(5 rows)
+
diff --git a/src/test/regress/sql/polymorphism.sql b/src/test/regress/sql/polymorphism.sql
index 218a0a72b3..c2bf14b48f 100644
--- a/src/test/regress/sql/polymorphism.sql
+++ b/src/test/regress/sql/polymorphism.sql
@@ -374,3 +374,19 @@ select f3, myaggn08b(f1) from t group by f3;
 select f3, myaggn09a(f1) from t group by f3;
 select f3, myaggn10a(f1) from t group by f3;
 select mysum2(f1, f1 + 1) from t;
+
+-- test inlining of polymorphic SQL functions
+create function bleat(int) returns int as $$
+begin
+  raise notice 'bleat %', $1;
+  return $1;
+end$$ language plpgsql;
+
+create function sql_if(bool, anyelement, anyelement) returns anyelement as $$
+select case when $1 then $2 else $3 end $$ language sql;
+
+-- Note this would fail with integer overflow, never mind wrong bleat() output,
+-- if the CASE expression were not successfully inlined
+select f1, sql_if(f1 > 0, bleat(f1), bleat(f1 + 1)) from int4_tbl;
+
+select q2, sql_if(q2 > 0, q2, q2 + 1) from int8_tbl;