diff --git a/papers/files.py b/papers/files.py
index 8be8a5d..8a0867f 100644
--- a/papers/files.py
+++ b/papers/files.py
@@ -108,7 +108,10 @@ def save_bibdata(bib_data, filepath):
 
 
 def save_meta(meta_data, filepath):
-    write_yamlfile(filepath, meta_data)
+    new_meta = meta_data.copy()
+    # Cannot store sets in yaml
+    new_meta['tags'] = list(new_meta['tags'])
+    write_yamlfile(filepath, new_meta)
 
 
 # is this function ever used? 08/06/2013
diff --git a/papers/paper.py b/papers/paper.py
index d0405a5..96577bd 100644
--- a/papers/paper.py
+++ b/papers/paper.py
@@ -20,7 +20,7 @@ CITEKEY_EXCLUDE_RE = re.compile('[%s]'
 
 BASE_META = {
     'external-document': None,
-    'tags': [],
+    'tags': set(),
     'notes': [],
     }
 
diff --git a/tests/fixtures.py b/tests/fixtures.py
index fb56d44..86bc7b6 100644
--- a/tests/fixtures.py
+++ b/tests/fixtures.py
@@ -8,6 +8,7 @@ turing1950.bibentry.fields['title'] = u'Computing machinery and intelligence.'
 turing1950.bibentry.fields['year'] = u'1950'
 turing1950.bibentry.persons['author'] = [Person(u'Alan Turing')]
 turing1950.citekey = turing1950.generate_citekey()
+turing1950.tags = ['computer', 'AI']
 
 
 doe2013 = Paper()
diff --git a/tests/test_paper.py b/tests/test_paper.py
index 43b37c6..c2c8446 100644
--- a/tests/test_paper.py
+++ b/tests/test_paper.py
@@ -24,7 +24,7 @@ entries:
 META = """
 external-document: null
 notes: []
-tags: []
+tags: ['AI', 'computer']
 """