diff --git a/moto/swf/exceptions.py b/moto/swf/exceptions.py
index bfbb96020..f58c0360a 100644
--- a/moto/swf/exceptions.py
+++ b/moto/swf/exceptions.py
@@ -30,3 +30,13 @@ class SWFDomainDeprecatedFault(SWFClientError):
         super(SWFDomainDeprecatedFault, self).__init__(
             domain_name,
             "com.amazonaws.swf.base.model#DomainDeprecatedFault")
+
+
+class SWFSerializationException(JSONResponseError):
+    def __init__(self):
+        message = "class java.lang.Foo can not be converted to an String (not a real SWF exception)"
+        __type = "com.amazonaws.swf.base.model#SerializationException"
+        super(SWFSerializationException, self).__init__(
+            400, "Bad Request",
+            body={"Message": message, "__type": __type}
+        )
diff --git a/moto/swf/models.py b/moto/swf/models.py
index 61ed508aa..880e00b3d 100644
--- a/moto/swf/models.py
+++ b/moto/swf/models.py
@@ -7,6 +7,7 @@ from .exceptions import (
     SWFUnknownResourceFault,
     SWFDomainAlreadyExistsFault,
     SWFDomainDeprecatedFault,
+    SWFSerializationException,
 )
 
 
@@ -40,12 +41,21 @@ class SWFBackend(BaseBackend):
             return matching[0]
         return None
 
+    def _check_string(self, parameter):
+        if not isinstance(parameter, basestring):
+            raise SWFSerializationException()
+
     def list_domains(self, status):
+        self._check_string(status)
         return [domain for domain in self.domains
                 if domain.status == status]
 
     def register_domain(self, name, workflow_execution_retention_period_in_days,
                         description=None):
+        self._check_string(name)
+        self._check_string(workflow_execution_retention_period_in_days)
+        if description:
+            self._check_string(description)
         if self._get_domain(name, ignore_empty=True):
             raise SWFDomainAlreadyExistsFault(name)
         domain = Domain(name, workflow_execution_retention_period_in_days,
@@ -53,12 +63,14 @@ class SWFBackend(BaseBackend):
         self.domains.append(domain)
 
     def deprecate_domain(self, name):
+        self._check_string(name)
         domain = self._get_domain(name)
         if domain.status == "DEPRECATED":
             raise SWFDomainDeprecatedFault(name)
         domain.status = "DEPRECATED"
 
     def describe_domain(self, name):
+        self._check_string(name)
         return self._get_domain(name)
 
 
diff --git a/tests/test_swf/test_swf.py b/tests/test_swf/test_swf.py
index 4f0617fc1..1a43e4cd0 100644
--- a/tests/test_swf/test_swf.py
+++ b/tests/test_swf/test_swf.py
@@ -7,6 +7,7 @@ from moto.swf.exceptions import (
     SWFUnknownResourceFault,
     SWFDomainAlreadyExistsFault,
     SWFDomainDeprecatedFault,
+    SWFSerializationException,
 )
 
 
@@ -15,7 +16,7 @@ from moto.swf.exceptions import (
 @mock_swf
 def test_register_domain():
     conn = boto.connect_swf("the_key", "the_secret")
-    conn.register_domain("test-domain", 60, description="A test domain")
+    conn.register_domain("test-domain", "60", description="A test domain")
 
     all_domains = conn.list_domains("REGISTERED")
     domain = all_domains["domainInfos"][0]
@@ -27,10 +28,10 @@ def test_register_domain():
 @mock_swf
 def test_register_already_existing_domain():
     conn = boto.connect_swf("the_key", "the_secret")
-    conn.register_domain("test-domain", 60, description="A test domain")
+    conn.register_domain("test-domain", "60", description="A test domain")
 
     with assert_raises(SWFDomainAlreadyExistsFault) as err:
-        conn.register_domain("test-domain", 60, description="A test domain")
+        conn.register_domain("test-domain", "60", description="A test domain")
 
     ex = err.exception
     ex.status.should.equal(400)
@@ -40,12 +41,27 @@ def test_register_already_existing_domain():
         "message": "test-domain"
     })
 
+@mock_swf
+def test_register_with_wrong_parameter_type():
+    conn = boto.connect_swf("the_key", "the_secret")
+
+    with assert_raises(SWFSerializationException) as err:
+        conn.register_domain("test-domain", 60, description="A test domain")
+
+    ex = err.exception
+    ex.status.should.equal(400)
+    ex.error_code.should.equal("SerializationException")
+    ex.body.should.equal({
+        "__type": "com.amazonaws.swf.base.model#SerializationException",
+        "Message": "class java.lang.Foo can not be converted to an String (not a real SWF exception)"
+    })
+
 
 # DeprecateDomain endpoint
 @mock_swf
 def test_deprecate_domain():
     conn = boto.connect_swf("the_key", "the_secret")
-    conn.register_domain("test-domain", 60, description="A test domain")
+    conn.register_domain("test-domain", "60", description="A test domain")
     conn.deprecate_domain("test-domain")
 
     all_domains = conn.list_domains("DEPRECATED")
@@ -56,7 +72,7 @@ def test_deprecate_domain():
 @mock_swf
 def test_deprecate_already_deprecated_domain():
     conn = boto.connect_swf("the_key", "the_secret")
-    conn.register_domain("test-domain", 60, description="A test domain")
+    conn.register_domain("test-domain", "60", description="A test domain")
     conn.deprecate_domain("test-domain")
 
     with assert_raises(SWFDomainDeprecatedFault) as err:
@@ -89,7 +105,7 @@ def test_deprecate_non_existent_domain():
 @mock_swf
 def test_describe_domain():
     conn = boto.connect_swf("the_key", "the_secret")
-    conn.register_domain("test-domain", 60, description="A test domain")
+    conn.register_domain("test-domain", "60", description="A test domain")
 
     domain = conn.describe_domain("test-domain")
     domain["configuration"]["workflowExecutionRetentionPeriodInDays"].should.equal("60")