diff --git a/source/shared/core_conn.cpp b/source/shared/core_conn.cpp
index b8ca39e3..5952ffb1 100644
--- a/source/shared/core_conn.cpp
+++ b/source/shared/core_conn.cpp
@@ -48,8 +48,9 @@ const int INFO_BUFFER_LEN = 256;
 // processor architectures
 const char* PROCESSOR_ARCH[] = { "x86", "x64", "ia64" };
 
-// ODBC driver name.
-std::vector<std::string> CONNECTION_STRING_DRIVER_NAME{ "Driver={ODBC Driver 17 for SQL Server};","Driver={ODBC Driver 13 for SQL Server};", "Driver={ODBC Driver 11 for SQL Server};" };
+// ODBC driver names.
+// the order of this list should match the order of DRIVER_VERSION enum
+std::vector<std::string> CONNECTION_STRING_DRIVER_NAME{ "Driver={ODBC Driver 13 for SQL Server};", "Driver={ODBC Driver 11 for SQL Server};", "Driver={ODBC Driver 17 for SQL Server};" };
 
 // default options if only the server is specified
 const char CONNECTION_STRING_DEFAULT_OPTIONS[] = "Mars_Connection={Yes};";
diff --git a/source/shared/core_sqlsrv.h b/source/shared/core_sqlsrv.h
index 2e72800f..e8e630a0 100644
--- a/source/shared/core_sqlsrv.h
+++ b/source/shared/core_sqlsrv.h
@@ -1033,13 +1033,13 @@ enum SERVER_VERSION {
 };
 
 // supported driver versions.
-enum DRIVER_VERSION {
-    ODBC_DRIVER_UNKNOWN = -1,
+// the latest RTWed ODBC is the first one
+enum DRIVER_VERSION : std::size_t{
     FIRST = 0,
-    ODBC_DRIVER_17 = FIRST,
-    ODBC_DRIVER_13 = 1,
-    ODBC_DRIVER_11 = 2,
-    LAST = ODBC_DRIVER_11
+    ODBC_DRIVER_13 = FIRST,
+    ODBC_DRIVER_11 = 1,
+    ODBC_DRIVER_17 = 2,
+    LAST = ODBC_DRIVER_17
 };
 
 // forward decl