diff --git a/ncdufmt/src/lib.rs b/ncdufmt/src/lib.rs
index 76cc0c4..42c10bd 100644
--- a/ncdufmt/src/lib.rs
+++ b/ncdufmt/src/lib.rs
@@ -3,8 +3,10 @@
 use num_traits::identities::One;
 use num_traits::identities::Zero;
 use serde::de;
+use serde::Serializer;
 // use serde::de::Error;
 use serde::de::Visitor;
+use serde::ser::SerializeSeq;
 use serde_repr::Deserialize_repr;
 use serde_repr::Serialize_repr;
 use std::ops::Not;
@@ -16,15 +18,28 @@ use serde::{Deserialize, Serialize};
 
 // This is based on https://dev.yorhel.nl/ncdu/jsonfmt
 
-#[derive(Serialize, Debug, PartialEq, Clone)]
+#[derive(Debug, PartialEq, Clone)]
 struct NcduFile {
     pub major_version: MajorVersion,
     pub minor_version: MinorVersion,
     pub header_metadata: HeaderMetadata,
-    #[serde(flatten)]
     pub contents: Directory,
 }
 
+impl Serialize for NcduFile {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut seq = serializer.serialize_seq(Some(4))?;
+        seq.serialize_element(&self.major_version)?;
+        seq.serialize_element(&self.minor_version)?;
+        seq.serialize_element(&self.header_metadata)?;
+        seq.serialize_element(&self.contents)?;
+        seq.end()
+    }
+}
+
 impl<'de> Deserialize<'de> for NcduFile {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
@@ -123,13 +138,34 @@ impl HeaderMetadata {
     }
 }
 
-#[derive(Serialize, Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Directory {
     info: InfoBlock,
-    #[serde(flatten)]
     contents: Vec<FileOrDirectory>,
 }
 
+impl Serialize for Directory {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        use serde::ser::Error;
+        let mut seq = serializer.serialize_seq(Some(
+            self.contents
+                .len()
+                .checked_add(1)
+                .ok_or_else(|| S::Error::custom("Directory contents too large"))?,
+        ))?;
+        // Add the info block first
+        seq.serialize_element(&self.info)?;
+        // Then any entries
+        for element in self.contents.iter() {
+            seq.serialize_element(element)?;
+        }
+        seq.end()
+    }
+}
+
 impl<'de> Deserialize<'de> for Directory {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
@@ -200,6 +236,7 @@ pub struct InfoBlock {
     /// Device ID. A unique ID within the context of the exported dump. Could be a serialization of lstat().st_dev, but could be randomly generated and used within this file
     ///
     /// Accepted values are in the range of 0 <= dev < 2^64.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     pub dev: Option<DeviceId>,
 
     /// Apparent filesize
@@ -261,17 +298,22 @@ pub struct InfoBlock {
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub struct ExtendedInfoBlock {
     /// Number, user ID who owns the file. Accepted values are in the range 0 <= uid < 2^31.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     uid: Option<u32>,
     /// Number, group ID who owns the file. Accepted values are in the range 0 <= uid < 2^31.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     gid: Option<u32>,
     /// Number, the raw file mode as returned by lstat(3). For Linux systems, see inode(7) for the interpretation of this field. Accepted range: 0 <= mode < 2^16.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     mode: Option<u16>,
     /// Number, last modification time as a UNIX timestamp. Accepted range: 0 <= mtime < 2^64. As of ncdu 1.16, this number may also include an (infinite precision) decimal part for fractional seconds, though the decimal part is (currently) discarded during import.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     mtime: Option<u64>,
 }
 
 #[cfg(test)]
 mod tests {
+    use serde_path_to_error;
     use std::fs;
 
     use super::*;
@@ -354,7 +396,6 @@ mod tests {
         .is_ok());
     }
 
-    use serde_path_to_error;
     #[test]
     fn test_simple_ncdu_output() {
         let input = fs::read_to_string("../sample-ncdu-output.json").unwrap();
@@ -365,7 +406,6 @@ mod tests {
                 e
             })
             .unwrap();
-        // let parsed = serde_path_to_error::from_str::<NcduFile>(&input).unwrap();
 
         assert_eq!(parsed.major_version, MajorVersion::Version1);
         assert_eq!(parsed.minor_version, MinorVersion::Minor2);
@@ -373,4 +413,17 @@ mod tests {
         assert_eq!(parsed.contents.info.name, "/tmp/tmp.2gWrgcHU4X");
         assert_eq!(parsed.contents.contents.len(), 2);
     }
+
+    #[test]
+    fn test_serialization() {
+        let input = fs::read_to_string("../sample-ncdu-output.json").unwrap();
+        let deserialized = serde_json::from_str::<NcduFile>(&input).unwrap();
+        let serialized = serde_json::to_string(&deserialized).unwrap();
+        let deserialized_again = serde_json::from_str::<NcduFile>(&serialized).unwrap();
+        let serialized_again = serde_json::to_string(&deserialized_again).unwrap();
+
+        assert_eq!(serialized, serialized_again);
+        assert_eq!(deserialized, deserialized_again);
+        assert_eq!(serialized, input);
+    }
 }