diff --git a/src/extlib/UdfBackwardCompatibility.sql b/src/extlib/UdfBackwardCompatibility.sql
index 2a265ae6b5..8131e385eb 100644
--- a/src/extlib/UdfBackwardCompatibility.sql
+++ b/src/extlib/UdfBackwardCompatibility.sql
@@ -14,13 +14,13 @@ create function frac (
 
 create function dow (
     val timestamp
-) returns varchar(53) character set utf8
+) returns varchar(53) character set none
     external name 'udf_compat!UC_dow'
     engine udr;
 
 create function sdow (
     val timestamp
-) returns varchar(13) character set utf8
+) returns varchar(13) character set none
     external name 'udf_compat!UC_sdow'
     engine udr;
 
diff --git a/src/misc/upgrade/v4.0/udf_replace.sql b/src/misc/upgrade/v4.0/udf_replace.sql
index b4253905a6..467381e088 100644
--- a/src/misc/upgrade/v4.0/udf_replace.sql
+++ b/src/misc/upgrade/v4.0/udf_replace.sql
@@ -56,14 +56,14 @@ if (exists(select * from RDB$FUNCTIONS where RDB$MODULE_NAME is not null and RDB
 if (exists(select * from RDB$FUNCTIONS where RDB$MODULE_NAME is not null and RDB$FUNCTION_NAME = 'DOW')) then execute statement
 'alter function dow (
     val timestamp
-) returns varchar(53) character set utf8
+) returns varchar(53) character set none
     external name ''udf_compat!UC_dow''
     engine udr';
 
 if (exists(select * from RDB$FUNCTIONS where RDB$MODULE_NAME is not null and RDB$FUNCTION_NAME = 'SDOW')) then execute statement
 'alter function sdow (
     val timestamp
-) returns varchar(13) character set utf8
+) returns varchar(13) character set none
     external name ''udf_compat!UC_sdow''
     engine udr';