diff --git a/src/serde_utils.rs b/src/serde_utils.rs
index 0c0b243d..8b74807e 100644
--- a/src/serde_utils.rs
+++ b/src/serde_utils.rs
@@ -60,6 +60,78 @@ pub mod btreemap {
     }
 }
 
+pub mod btreemap_byte_values {
+    //! Module for serialization of BTreeMaps with Vec<u8> values because
+    //! serde_json will not serialize hashmaps with non-string keys be default.
+    #![allow(missing_docs)]
+
+    // NOTE: This module can be exactly copied to use with HashMap.
+
+    use ::std::collections::BTreeMap;
+    use serde;
+
+    /// A custom key-value pair type that serialized the bytes as hex.
+    #[derive(Debug, Deserialize)]
+    struct OwnedPair<T>(
+        T,
+        #[serde(deserialize_with = "::serde_utils::hex_bytes::deserialize")]
+        Vec<u8>,
+    );
+
+    /// A custom key-value pair type that serialized the bytes as hex.
+    #[derive(Debug, Serialize)]
+    struct BorrowedPair<'a, T: 'static>(
+        &'a T,
+        #[serde(serialize_with = "::serde_utils::hex_bytes::serialize")]
+        &'a [u8],
+    );
+
+    pub fn serialize<S, T>(v: &BTreeMap<T, Vec<u8>>, s: S)
+        -> Result<S::Ok, S::Error> where
+        S: serde::Serializer,
+        T: serde::Serialize + ::std::hash::Hash + Eq + Ord + 'static,
+    {
+        use serde::ser::SerializeSeq;
+
+        let mut seq = s.serialize_seq(Some(v.len()))?;
+        for (key, value) in v.iter() {
+            seq.serialize_element(&BorrowedPair(key, value))?;
+        }
+        seq.end()
+    }
+
+    pub fn deserialize<'de, D, T>(d: D)
+        -> Result<BTreeMap<T, Vec<u8>>, D::Error> where
+        D: serde::Deserializer<'de>,
+        T: serde::Deserialize<'de> + ::std::hash::Hash + Eq + Ord,
+    {
+        use ::std::marker::PhantomData;
+
+        struct Visitor<T>(PhantomData<T>);
+        impl<'de, T> serde::de::Visitor<'de> for Visitor<T> where
+            T: serde::Deserialize<'de> + ::std::hash::Hash + Eq + Ord,
+        {
+            type Value = BTreeMap<T, Vec<u8>>;
+
+            fn expecting(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                write!(f, "a sequence of pairs")
+            }
+
+            fn visit_seq<A: serde::de::SeqAccess<'de>>(self, mut a: A)
+                -> Result<Self::Value, A::Error>
+            {
+                let mut ret = BTreeMap::new();
+                while let Option::Some(OwnedPair(key, value)) = a.next_element()? {
+                    ret.insert(key, value);
+                }
+                Ok(ret)
+            }
+        }
+
+        d.deserialize_seq(Visitor(PhantomData))
+    }
+}
+
 pub mod hex_bytes {
     //! Module for serialization of byte arrays as hex strings.
     #![allow(missing_docs)]
diff --git a/src/util/psbt/map/global.rs b/src/util/psbt/map/global.rs
index aa5d6254..d3b9c5b4 100644
--- a/src/util/psbt/map/global.rs
+++ b/src/util/psbt/map/global.rs
@@ -49,10 +49,10 @@ pub struct Global {
     #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
     pub xpub: BTreeMap<ExtendedPubKey, KeySource>,
     /// Global proprietary key-value pairs.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub proprietary: BTreeMap<raw::ProprietaryKey, Vec<u8>>,
     /// Unknown global key-value pairs.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub unknown: BTreeMap<raw::Key, Vec<u8>>,
 }
 
diff --git a/src/util/psbt/map/input.rs b/src/util/psbt/map/input.rs
index 112eae9a..4f42a9ac 100644
--- a/src/util/psbt/map/input.rs
+++ b/src/util/psbt/map/input.rs
@@ -70,7 +70,7 @@ pub struct Input {
     pub witness_utxo: Option<TxOut>,
     /// A map from public keys to their corresponding signature as would be
     /// pushed to the stack from a scriptSig or witness.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub partial_sigs: BTreeMap<PublicKey, Vec<u8>>,
     /// The sighash type to be used for this input. Signatures for this input
     /// must use the sighash type.
@@ -99,10 +99,10 @@ pub struct Input {
     /// HAS256 hash to preimage map
     pub hash256_preimages: BTreeMap<sha256d::Hash, Vec<u8>>,
     /// Proprietary key-value pairs for this input.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub proprietary: BTreeMap<raw::ProprietaryKey, Vec<u8>>,
     /// Unknown key-value pairs for this input.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub unknown: BTreeMap<raw::Key, Vec<u8>>,
 }
 
diff --git a/src/util/psbt/map/output.rs b/src/util/psbt/map/output.rs
index 34861ba5..6a082467 100644
--- a/src/util/psbt/map/output.rs
+++ b/src/util/psbt/map/output.rs
@@ -47,10 +47,10 @@ pub struct Output {
     #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
     pub bip32_derivation: BTreeMap<PublicKey, KeySource>,
     /// Proprietary key-value pairs for this output.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub proprietary: BTreeMap<raw::ProprietaryKey, Vec<u8>>,
     /// Unknown key-value pairs for this output.
-    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap"))]
+    #[cfg_attr(feature = "serde", serde(with = "::serde_utils::btreemap_byte_values"))]
     pub unknown: BTreeMap<raw::Key, Vec<u8>>,
 }