diff --git a/hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQL81Dialect.java b/hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQL81Dialect.java
index 52a6931f99..446ffab574 100644
--- a/hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQL81Dialect.java
+++ b/hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQL81Dialect.java
@@ -119,7 +119,7 @@ public class PostgreSQL81Dialect extends Dialect {
 		registerFunction( "to_ascii", new StandardSQLFunction("to_ascii") );
 		registerFunction( "quote_ident", new StandardSQLFunction("quote_ident", StandardBasicTypes.STRING) );
 		registerFunction( "quote_literal", new StandardSQLFunction("quote_literal", StandardBasicTypes.STRING) );
-		registerFunction( "md5", new StandardSQLFunction("md5") );
+		registerFunction( "md5", new StandardSQLFunction("md5", StandardBasicTypes.STRING) );
 		registerFunction( "ascii", new StandardSQLFunction("ascii", StandardBasicTypes.INTEGER) );
 		registerFunction( "char_length", new StandardSQLFunction("char_length", StandardBasicTypes.LONG) );
 		registerFunction( "bit_length", new StandardSQLFunction("bit_length", StandardBasicTypes.LONG) );