diff --git a/src/AWSCredentials.jl b/src/AWSCredentials.jl
index a9639a2..d2eed3a 100644
--- a/src/AWSCredentials.jl
+++ b/src/AWSCredentials.jl
@@ -29,7 +29,7 @@ The `AWSCredentials()` constructor tries to load local Credentials from
 environment variables, `~/.aws/credentials` or EC2 instance credentials.
 """
 
-type AWSCredentials
+mutable struct AWSCredentials
     access_key_id::String
     secret_key::String
     token::String