diff --git a/README.rst b/README.rst
index 1615d76..31cfede 100644
--- a/README.rst
+++ b/README.rst
@@ -50,6 +50,25 @@ As a standalone package
     result = interpolate_dict(data, store)
     assert result[key] == 'my-secret-password'
 
+Using custom configuration parameters
+
+.. code-block:: python
+
+    from param_store import EC2ParameterStore
+    from param_store import interpolate_dict
+
+    data = {
+        'key': 'my-secret-{{ parameter-1 }}'
+    }
+
+    aws_config = {
+        "region_name": "us-east-1",
+        "aws_access_key_id": "YOUR_NEW_ACCESS_KEY"
+    }
+
+    store = EC2ParameterStore(aws_config=aws_config)
+    result = interpolate_dict(data, store)
+    assert result[key] == 'my-secret-password'
 
 In combination with django-environ
 
diff --git a/src/param_store/stores.py b/src/param_store/stores.py
index b9cbabe..e3ee1bc 100644
--- a/src/param_store/stores.py
+++ b/src/param_store/stores.py
@@ -10,10 +10,13 @@ def load_values(self, items):
 
 
 class EC2ParameterStore(BaseStore):
-    def __init__(self):
+    def __init__(self, aws_config=None):
         import boto3
 
-        self.client = boto3.client("ssm")
+        if isinstance(aws_config, dict):
+            self.client = boto3.client("ssm", **aws_config)
+        else:
+            self.client = boto3.client("ssm")
 
     def load_values(self, items):
         """Load the parameters from the AWS Parameter Store.
diff --git a/tests/test_stores.py b/tests/test_stores.py
index 5bb3268..f8f188c 100644
--- a/tests/test_stores.py
+++ b/tests/test_stores.py
@@ -39,6 +39,23 @@ def test_ec2_parameter_store_many():
     assert result == data
 
 
+@moto.mock_ssm
+def test_ec2_parameter_store_different_parameters():
+    right_region_name = "eu-west-1"
+    key_wanted = "key-eu-weast-1"
+    ssm = boto3.client("ssm", region_name=right_region_name)
+    ssm.put_parameter(Name=key_wanted, Value="hoi", Type="SecureString")
+
+    store = EC2ParameterStore(aws_config={"region_name": "us-east-1"})
+    result = store.load_values([key_wanted])
+    assert key_wanted not in result
+
+    store = EC2ParameterStore(aws_config={"region_name": right_region_name})
+    result = store.load_values([key_wanted])
+    assert key_wanted in result
+    assert result == {key_wanted: "hoi"}
+
+
 def test_file_parameter_store(tmpdir):
     secret_path = tmpdir.mkdir("secrets")
     secret_path.join("key").write("hoi")