diff --git a/pypyodbc.py b/pypyodbc.py
index 0f38a6e..69f10f1 100644
--- a/pypyodbc.py
+++ b/pypyodbc.py
@@ -639,7 +639,7 @@ def Decimal_cvt(x):
 SQL_BIT             : (bool,                lambda x:x == BYTE_1,       SQL_C_CHAR,         create_buffer,      2     ,         False         ),
 SQL_WCHAR           : (unicode,             lambda x: x,                SQL_C_WCHAR,        create_buffer_u,    2048  ,         False          ),
 SQL_WVARCHAR        : (unicode,             lambda x: x,                SQL_C_WCHAR,        create_buffer_u,    2048  ,         False          ),
-SQL_GUID            : (str,                 str,                        SQL_C_CHAR,         create_buffer,      2048  ,         False         ),
+SQL_GUID            : (str,                 lambda x: x,                SQL_C_CHAR,         create_buffer,      2048  ,         False         ),
 SQL_WLONGVARCHAR    : (unicode,             lambda x: x,                SQL_C_WCHAR,        create_buffer_u,    20500 ,         True          ),
 SQL_TYPE_DATE       : (datetime.date,       dt_cvt,                     SQL_C_CHAR,         create_buffer,      30    ,         False         ),
 SQL_TYPE_TIME       : (datetime.time,       tm_cvt,                     SQL_C_CHAR,         create_buffer,      20    ,         False         ),