diff --git a/src/common/composite_file.rs b/src/common/composite_file.rs
index b092f0bce..39db0bbcb 100644
--- a/src/common/composite_file.rs
+++ b/src/common/composite_file.rs
@@ -27,7 +27,7 @@ impl<W: Write> CompositeWrite<W> {
         &mut self.write
     }
 
-    pub fn close(&mut self) -> io::Result<()> {
+    pub fn close(mut self) -> io::Result<()> {
         let footer_offset = self.write.written_bytes();
         VInt(self.offsets.len() as u64).serialize(&mut self.write)?;
 
diff --git a/src/fastfield/mod.rs b/src/fastfield/mod.rs
index cff0f151e..fc69f6ddf 100644
--- a/src/fastfield/mod.rs
+++ b/src/fastfield/mod.rs
@@ -97,17 +97,15 @@ mod tests {
         {
             assert_eq!(source.len(), 35 as usize);
         }
-        // TODO uncomment
-        /*
         {
-            let fast_field_readers = FastFieldsReader::from_source(source).unwrap();
+            let composite_file = CompositeFile::open(source).unwrap();
+            let field_source = composite_file.open_read(*FIELD).unwrap();
             let fast_field_reader: U64FastFieldReader =
-                fast_field_readers.open_reader(*FIELD).unwrap();
+                U64FastFieldReader::open(field_source);
             assert_eq!(fast_field_reader.get(0), 13u64);
             assert_eq!(fast_field_reader.get(1), 14u64);
             assert_eq!(fast_field_reader.get(2), 2u64);
         }
-        */
     }
 
     #[test]
diff --git a/src/fastfield/serializer.rs b/src/fastfield/serializer.rs
index 590aee84a..62dd7cba1 100644
--- a/src/fastfield/serializer.rs
+++ b/src/fastfield/serializer.rs
@@ -59,7 +59,7 @@ impl FastFieldSerializer {
     /// Closes the serializer
     ///
     /// After this call the data must be persistently save on disk.
-    pub fn close(mut self) -> io::Result<()> {
+    pub fn close(self) -> io::Result<()> {
         self.composite_write.close()
     }
 }
diff --git a/src/postings/serializer.rs b/src/postings/serializer.rs
index 087baed3d..76c1f1f6b 100644
--- a/src/postings/serializer.rs
+++ b/src/postings/serializer.rs
@@ -112,7 +112,7 @@ impl InvertedIndexSerializer {
     }
 
     /// Closes the serializer.
-    pub fn close(mut self) -> io::Result<()> {
+    pub fn close(self) -> io::Result<()> {
         self.terms_write.close()?;
         self.postings_write.close()?;
         self.positions_write.close()?;
@@ -223,9 +223,6 @@ impl<'a> FieldSerializer<'a> {
     }
 }
 
-// TODO is the last term always closed?
-
-
 
 struct PostingsSerializer<W: Write> {
     postings_write: CountingWriter<W>,