diff --git a/tablib/formats/_csv.py b/tablib/formats/_csv.py
index 3cda71b..c5d3202 100644
--- a/tablib/formats/_csv.py
+++ b/tablib/formats/_csv.py
@@ -49,7 +49,7 @@ def import_set(dset, in_stream, headers=True):
 def detect(stream):
     """Returns True if given stream is valid CSV."""
     try:
-        csv.Sniffer().sniff(stream)
+        csv.Sniffer().sniff(stream, delimiters=',')
         return True
     except (csv.Error, TypeError):
         return False
diff --git a/tablib/formats/_yaml.py b/tablib/formats/_yaml.py
index e2ccf46..0052b0f 100644
--- a/tablib/formats/_yaml.py
+++ b/tablib/formats/_yaml.py
@@ -26,12 +26,12 @@ extensions = ('yaml', 'yml')
 def export_set(dataset):
     """Returns YAML representation of Dataset."""
 
-    return yaml.dump(dataset._package(ordered=False))
+    return yaml.safe_dump(dataset._package(ordered=False))
 
 
 def export_book(databook):
     """Returns YAML representation of Databook."""
-    return yaml.dump(databook._package())
+    return yaml.safe_dump(databook._package(ordered=False))
 
 
 def import_set(dset, in_stream):
diff --git a/test_tablib.py b/test_tablib.py
index 526370a..70e6051 100755
--- a/test_tablib.py
+++ b/test_tablib.py
@@ -493,10 +493,12 @@ class TablibTestCase(unittest.TestCase):
         _yaml = '- {age: 90, first_name: John, last_name: Adams}'
         _json = '[{"last_name": "Adams","age": 90,"first_name": "John"}]'
         _csv = '1,2,3\n4,5,6\n7,8,9\n'
+        _tsv = '1\t2\t3\n4\t5\t6\n7\t8\t9\n'
         _bunk = '¡¡¡¡¡¡---///\n\n\n¡¡£™∞¢£§∞§¶•¶ª∞¶•ªº••ª–º§•†•§º¶•†¥ª–º•§ƒø¥¨©πƒø†ˆ¥ç©¨√øˆ¥≈†ƒ¥ç©ø¨çˆ¥ƒçø¶'
 
         self.assertEqual(tablib.detect(_yaml)[0], tablib.formats.yaml)
         self.assertEqual(tablib.detect(_csv)[0], tablib.formats.csv)
+        self.assertEqual(tablib.detect(_tsv)[0], tablib.formats.tsv)
         self.assertEqual(tablib.detect(_json)[0], tablib.formats.json)
         self.assertEqual(tablib.detect(_bunk)[0], None)