diff --git a/picard/version.py b/picard/version.py
index a44201fa5..dad2fc978 100644
--- a/picard/version.py
+++ b/picard/version.py
@@ -37,40 +37,45 @@ class Version(tuple):
         'final': 4
     }
 
-    def __new__(cls, major, minor, patch, identifier='final', revision=0):
+    def __new__(cls, major, minor, patch=0, identifier='final', revision=0):
         if identifier not in cls.valid_identifiers():
             raise VersionError("Should be either 'final', 'dev', 'alpha', 'beta' or 'rc'")
         identifier = {'a': 'alpha', 'b': 'beta'}.get(identifier, identifier)
+        try:
+            major = int(major)
+            minor = int(minor)
+            patch = int(patch)
+            revision = int(revision)
+        except (TypeError, ValueError):
+            raise VersionError("major, minor, patch and revision must be integer values")
         return super(Version, cls).__new__(cls, (major, minor, patch, identifier, revision))
 
     @classmethod
     def from_string(cls, version_str):
-        m = cls._version_re.search(version_str)
-        if m:
-            g = m.groups()
-            if g[2] is None:
-                return Version(int(g[0]), int(g[1]), 0, 'final', 0)
-            if g[3] is None:
-                return Version(int(g[0]), int(g[1]), int(g[2]), 'final', 0)
-            return Version(int(g[0]), int(g[1]), int(g[2]), g[3], int(g[4]))
+        match = cls._version_re.search(version_str)
+        if match:
+            (major, minor, patch, identifier, revision) = match.groups()
+            major = int(major)
+            minor = int(minor)
+            if patch is None:
+                return Version(major, minor)
+            patch = int(patch)
+            if identifier is None:
+                return Version(major, minor, patch)
+            revision = int(revision)
+            return Version(major, minor, patch, identifier, revision)
         raise VersionError("String '%s' does not match regex '%s'" % (version_str,
                                                                       cls._version_re.pattern))
 
     @classmethod
     def valid_identifiers(cls):
-        return cls._identifiers.keys()
+        return set(cls._identifiers.keys())
 
     def to_string(self, short=False):
-        _version = []
-        for p in self:
-            try:
-                n = int(p)
-            except ValueError:
-                n = p
-            _version.append(n)
-        if short and _version[3] in ('alpha', 'beta'):
-            _version[3] = _version[3][:1]
-        version = tuple(_version)
+        if short and self[3] in ('alpha', 'beta'):
+            version = (self[0], self[1], self[2], self[3][:1], self[4])
+        else:
+            version = self
         if short and version[3] == 'final':
             if version[2] == 0:
                 version_str = '%d.%d' % version[:2]
diff --git a/test/test_versions.py b/test/test_versions.py
index 4178b9c91..5a043266c 100644
--- a/test/test_versions.py
+++ b/test/test_versions.py
@@ -99,6 +99,12 @@ class VersionsTest(PicardTestCase):
             b = api_versions_tuple[i+1]
             self.assertLess(a, b)
 
+    def test_version_invalid_new(self):
+        self.assertRaises(VersionError, Version, '1', 'a')
+        self.assertRaises(VersionError, Version, None, 0)
+        self.assertRaises(VersionError, Version, 1, 0, 0, 'final', None)
+        self.assertRaises(VersionError, Version, 1, 0, 0, 'invalid', 0)
+
     def test_sortkey(self):
         self.assertEqual((2, 1, 3, 4, 2), Version(2, 1, 3, 'final', 2).sortkey)
         self.assertEqual((2, 0, 0, 1, 0), Version(2, 0, 0, 'a', 0).sortkey)