diff --git a/Dapper/SqlMapper.cs b/Dapper/SqlMapper.cs
index ee49c2abd..b8a8cd29e 100644
--- a/Dapper/SqlMapper.cs
+++ b/Dapper/SqlMapper.cs
@@ -367,7 +367,7 @@ public static void SetDbType(IDataParameter parameter, object value)
             handler = null;
             var nullUnderlyingType = Nullable.GetUnderlyingType(type);
             if (nullUnderlyingType != null) type = nullUnderlyingType;
-            if (type.IsEnum && !typeMap.ContainsKey(type))
+            if (type.IsEnum && !typeMap.ContainsKey(type) && !typeHandlers.ContainsKey(type))
             {
                 type = Enum.GetUnderlyingType(type);
             }