diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index eea4239854..5f23f2afac 100644
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -2946,6 +2946,10 @@ numeric_fac(PG_FUNCTION_ARGS)
 	NumericVar	fact;
 	NumericVar	result;
 
+	if (num < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("factorial of a negative number is undefined")));
 	if (num <= 1)
 	{
 		res = make_result(&const_one);
diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
index b255be7c85..2f3ecb50a7 100644
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -2345,14 +2345,6 @@ SELECT 0!;
 (1 row)
 
 SELECT -4!;
- ?column? 
-----------
-        1
-(1 row)
-
+ERROR:  factorial of a negative number is undefined
 SELECT factorial(-4);
- factorial 
------------
-         1
-(1 row)
-
+ERROR:  factorial of a negative number is undefined