diff --git a/src/common/backend/utils/adt/formatting.cpp b/src/common/backend/utils/adt/formatting.cpp
index 0367cf913c5a2cf2ddd14c2187a32a25334e01fc..71d4b7869ac7e02c38e6570c2d8cadfbbffeb18d 100644
--- a/src/common/backend/utils/adt/formatting.cpp
+++ b/src/common/backend/utils/adt/formatting.cpp
@@ -4638,7 +4638,9 @@ Datum blob_to_char_default(PG_FUNCTION_ARGS)
 
 Datum unknown_to_char2(PG_FUNCTION_ARGS)
 {
-    Datum result = DirectFunctionCall2(numeric_to_char, PG_GETARG_DATUM(0), PG_GETARG_DATUM(1));
+    Datum arg0 = DirectFunctionCall3(numeric_in, PG_GETARG_DATUM(0), NUMERICOID, -1);
+    Datum arg1 = DirectFunctionCall1(textin, PG_GETARG_DATUM(1));
+    Datum result = DirectFunctionCall2(numeric_to_char, arg0, arg1);
     PG_RETURN_DATUM(result);
 }
 
diff --git a/src/test/regress/expected/hw_functions.out b/src/test/regress/expected/hw_functions.out
index d19360d0be100aa7cb0926a0994de5eef18d1d60..f8604a9272034a530aeeb70148f1e51e00dbe9bc 100644
--- a/src/test/regress/expected/hw_functions.out
+++ b/src/test/regress/expected/hw_functions.out
@@ -957,4 +957,10 @@ SELECT to_char('','');
  
 (1 row)
 
+SELECT to_char('2020-08-26 14:57:33','yyyy-mon-dd hh24:mi:ss');
+ERROR:  invalid input syntax for type numeric: "2020-08-26 14:57:33"
+CONTEXT:  referenced column: to_char
+SELECT to_char('2020','yyyy-mon-dd hh24:mi:ss');
+ERROR:  multiple decimal points
+CONTEXT:  referenced column: to_char
 drop schema basefunc cascade;
diff --git a/src/test/regress/sql/hw_functions.sql b/src/test/regress/sql/hw_functions.sql
index f18e611f02aace0928dbb6c77c5daaa2a8a6fb2b..d637c951c6b8958e5400354917e4f4834fb6edce 100644
--- a/src/test/regress/sql/hw_functions.sql
+++ b/src/test/regress/sql/hw_functions.sql
@@ -373,5 +373,7 @@ SELECT to_char(c1, 873) FROM blob_table ;
 DROP TABLE blob_table;
 DROP TABLE blob_t;
 SELECT to_char('','');
+SELECT to_char('2020-08-26 14:57:33','yyyy-mon-dd hh24:mi:ss');
+SELECT to_char('2020','yyyy-mon-dd hh24:mi:ss');
 
 drop schema basefunc cascade;