diff --git a/graphene_sqlalchemy/tests/test_types.py b/graphene_sqlalchemy/tests/test_types.py
index bf563b6e..e9baf206 100644
--- a/graphene_sqlalchemy/tests/test_types.py
+++ b/graphene_sqlalchemy/tests/test_types.py
@@ -1,11 +1,14 @@
 import mock
 import pytest
 import six  # noqa F401
+import sqlalchemy.exc
+import sqlalchemy.orm.exc
 
 from graphene import (Dynamic, Field, GlobalID, Int, List, Node, NonNull,
                       ObjectType, Schema, String)
 from graphene.relay import Connection
 
+from .. import utils
 from ..converter import convert_sqlalchemy_composite
 from ..fields import (SQLAlchemyConnectionField,
                       UnsortedSQLAlchemyConnectionField, createConnectionField,
@@ -492,3 +495,65 @@ class Meta:
 def test_deprecated_createConnectionField():
     with pytest.warns(DeprecationWarning):
         createConnectionField(None)
+
+
+@mock.patch(utils.__name__ + '.class_mapper')
+def test_unique_errors_propagate(class_mapper_mock):
+    # Define unique error to detect
+    class UniqueError(Exception):
+        pass
+
+    # Mock class_mapper effect
+    class_mapper_mock.side_effect = UniqueError
+
+    # Make sure that errors are propagated from class_mapper when instantiating new classes
+    error = None
+    try:
+        class ArticleOne(SQLAlchemyObjectType):
+            class Meta(object):
+                model = Article
+    except UniqueError as e:
+        error = e
+
+    # Check that an error occured, and that it was the unique error we gave
+    assert error is not None
+    assert isinstance(error, UniqueError)
+
+
+@mock.patch(utils.__name__ + '.class_mapper')
+def test_argument_errors_propagate(class_mapper_mock):
+    # Mock class_mapper effect
+    class_mapper_mock.side_effect = sqlalchemy.exc.ArgumentError
+
+    # Make sure that errors are propagated from class_mapper when instantiating new classes
+    error = None
+    try:
+        class ArticleTwo(SQLAlchemyObjectType):
+            class Meta(object):
+                model = Article
+    except sqlalchemy.exc.ArgumentError as e:
+        error = e
+
+    # Check that an error occured, and that it was the unique error we gave
+    assert error is not None
+    assert isinstance(error, sqlalchemy.exc.ArgumentError)
+
+
+@mock.patch(utils.__name__ + '.class_mapper')
+def test_unmapped_errors_reformat(class_mapper_mock):
+    # Mock class_mapper effect
+    class_mapper_mock.side_effect = sqlalchemy.orm.exc.UnmappedClassError(object)
+
+    # Make sure that errors are propagated from class_mapper when instantiating new classes
+    error = None
+    try:
+        class ArticleThree(SQLAlchemyObjectType):
+            class Meta(object):
+                model = Article
+    except ValueError as e:
+        error = e
+
+    # Check that an error occured, and that it was the unique error we gave
+    assert error is not None
+    assert isinstance(error, ValueError)
+    assert "You need to pass a valid SQLAlchemy Model" in str(error)
diff --git a/graphene_sqlalchemy/types.py b/graphene_sqlalchemy/types.py
index ff22cded..1a1dbd33 100644
--- a/graphene_sqlalchemy/types.py
+++ b/graphene_sqlalchemy/types.py
@@ -207,10 +207,10 @@ def __init_subclass_with_meta__(
         _meta=None,
         **options
     ):
-        assert is_mapped_class(model), (
-            "You need to pass a valid SQLAlchemy Model in " '{}.Meta, received "{}".'
-        ).format(cls.__name__, model)
-
+        if not is_mapped_class(model):
+            raise ValueError(
+                "You need to pass a valid SQLAlchemy Model in " '{}.Meta, received "{}".'.format(cls.__name__, model)
+            )
         if not registry:
             registry = get_global_registry()
 
diff --git a/graphene_sqlalchemy/utils.py b/graphene_sqlalchemy/utils.py
index 7139eefc..7a47bde8 100644
--- a/graphene_sqlalchemy/utils.py
+++ b/graphene_sqlalchemy/utils.py
@@ -26,7 +26,12 @@ def get_query(model, context):
 def is_mapped_class(cls):
     try:
         class_mapper(cls)
-    except (ArgumentError, UnmappedClassError):
+    except ArgumentError as error:
+        # Only handle ArgumentErrors for non-class objects
+        if "Class object expected" in str(error):
+            return False
+        raise error
+    except UnmappedClassError:
         return False
     else:
         return True