diff --git a/sparkpost/transmissions.py b/sparkpost/transmissions.py
index 3586e2f..667b891 100644
--- a/sparkpost/transmissions.py
+++ b/sparkpost/transmissions.py
@@ -4,6 +4,7 @@
 from email.utils import parseaddr
 
 from .base import Resource
+from .exceptions import SparkPostException
 
 
 try:
@@ -137,6 +138,10 @@ def _parse_address(self, address):
         return parsed_address
 
     def _extract_recipients(self, recipients):
+
+        if not (isinstance(recipients, (list, dict))):
+            raise SparkPostException('recipients must be a list or dict')
+
         formatted_recipients = []
         for recip in recipients:
             if isinstance(recip, string_types):
diff --git a/test/test_transmissions.py b/test/test_transmissions.py
index 9847fb2..a5d6ae0 100644
--- a/test/test_transmissions.py
+++ b/test/test_transmissions.py
@@ -9,7 +9,7 @@
 
 from sparkpost import SparkPost
 from sparkpost import Transmissions
-from sparkpost.exceptions import SparkPostAPIException
+from sparkpost.exceptions import SparkPostAPIException, SparkPostException
 
 
 def test_translate_keys_with_list():
@@ -29,6 +29,12 @@ def test_translate_keys_with_recips():
                                      {'address': {'email': 'foobar'}}]
 
 
+def test_exceptions_for_recipients():
+    t = Transmissions('uri', 'key')
+    with pytest.raises(SparkPostException):
+        t._translate_keys(recipients='test')
+
+
 def test_translate_keys_with_unicode_recips():
     t = Transmissions('uri', 'key')
     results = t._translate_keys(recipients=[u'unicode_email@example.com',