diff --git a/beets/library.py b/beets/library.py
index 65c27a0c9..1ec08c7a1 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -159,6 +159,28 @@ ITEM_DEFAULT_FIELDS = ARTIST_DEFAULT_FIELDS + ALBUM_DEFAULT_FIELDS + \
 # Special path format key.
 PF_KEY_DEFAULT = 'default'
 
+# Convert 'true' and 'false' to correspondent boolean
+def _str_to_bool(value):
+    if value.lower() == 'true':
+        return True
+    if value.lower() == 'false':
+        return False
+    raise ValueError('could not convert string to bool: {0}'.format(value))
+
+# Mapping the correspondent Python constructor to SQLite field types
+CONSTRUCTOR_MAPPING = {
+    'int': int,
+    'bool': _str_to_bool,
+    'real': float,
+}
+
+# Convert a string (from user input) to the correct Python type
+def _convert_type(fields, key, value):
+    sqlite_type = [f[1] for f in fields if f[0] == key][0]
+    if value and sqlite_type in CONSTRUCTOR_MAPPING:
+        constructor = CONSTRUCTOR_MAPPING[sqlite_type]
+        return constructor(value)
+    return value
 
 # Logger.
 log = logging.getLogger('beets')
@@ -642,7 +664,7 @@ class AnyFieldQuery(CollectionQuery):
             if subq.match(item):
                 return True
         return False
-    
+
 class MutableCollectionQuery(CollectionQuery):
     """A collection query whose subqueries may be modified after the
     query is initialized.
diff --git a/beets/ui/commands.py b/beets/ui/commands.py
index 5560e1d79..e9e36d83e 100644
--- a/beets/ui/commands.py
+++ b/beets/ui/commands.py
@@ -990,13 +990,14 @@ default_commands.append(version_cmd)
 def modify_items(lib, mods, query, write, move, album, confirm):
     """Modifies matching items according to key=value assignments."""
     # Parse key=value specifications into a dictionary.
+    fields = library.ALBUM_FIELDS if album else library.ITEM_FIELDS
     allowed_keys = library.ALBUM_KEYS if album else library.ITEM_KEYS_WRITABLE
     fsets = {}
     for mod in mods:
         key, value = mod.split('=', 1)
         if key not in allowed_keys:
             raise ui.UserError('"%s" is not a valid field' % key)
-        fsets[key] = value
+        fsets[key] = library._convert_type(fields, key, value)
 
     # Get the items to modify.
     items, albums = _do_query(lib, query, album, False)