diff --git a/zebra-chain/Cargo.toml b/zebra-chain/Cargo.toml
index 4e575cd0..767fc56f 100644
--- a/zebra-chain/Cargo.toml
+++ b/zebra-chain/Cargo.toml
@@ -20,3 +20,4 @@ ed25519-zebra = "0.1"
 
 [dev-dependencies]
 proptest = "0.9"
+proptest-derive = "0.1.0"
diff --git a/zebra-chain/proptest-regressions/types.txt b/zebra-chain/proptest-regressions/types.txt
new file mode 100644
index 00000000..8d37aacf
--- /dev/null
+++ b/zebra-chain/proptest-regressions/types.txt
@@ -0,0 +1,8 @@
+# Seeds for failure cases proptest has generated in the past. It is
+# automatically read and these particular cases re-run before any
+# novel cases are generated.
+#
+# It is recommended to check this file in to source control so that
+# everyone who runs the test benefits from these saved cases.
+cc 77e4c5adc662baed850ecd3142ba2d61fa50d7dc7f75e56a1cb4ac6307a9a7e2 # shrinks to locktime = Height(BlockHeight(0))
+cc dbb060756c70411d81f49af9c742cbea259314ddf03440ff00ef62770047e304 # shrinks to locktime = Time(2019-12-19T19:48:42.288928Z)
diff --git a/zebra-chain/src/types.rs b/zebra-chain/src/types.rs
index bf06981e..a355b982 100644
--- a/zebra-chain/src/types.rs
+++ b/zebra-chain/src/types.rs
@@ -8,6 +8,8 @@ use std::{
 use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
 use chrono::{DateTime, TimeZone, Utc};
 use hex;
+#[cfg(test)]
+use proptest_derive::Arbitrary;
 
 use crate::serialization::{
     ReadZcashExt, SerializationError, WriteZcashExt, ZcashDeserialize, ZcashSerialize,
@@ -124,3 +126,47 @@ mod tests {
         assert_eq!(format!("{:?}", checksum), "Sha256dChecksum(\"9595c9df\")");
     }
 }
+
+#[cfg(test)]
+mod proptest {
+
+    use std::io::Cursor;
+
+    use chrono::Utc;
+    use proptest::prelude::*;
+
+    use super::{BlockHeight, LockTime};
+    use crate::serialization::{ZcashDeserialize, ZcashSerialize};
+
+    impl Arbitrary for LockTime {
+        type Parameters = ();
+
+        fn arbitrary_with(_args: ()) -> Self::Strategy {
+            prop_oneof![
+                (0u32..500_000_000_u32).prop_map(|n| LockTime::Height(BlockHeight(n))),
+                Just(LockTime::Time(Utc::now()))
+            ]
+            .boxed()
+        }
+
+        type Strategy = BoxedStrategy<Self>;
+    }
+
+    proptest! {
+
+        #[test]
+        fn locktime_roundtrip(locktime in any::<LockTime>()) {
+            let mut bytes = Cursor::new(Vec::new());
+            locktime.zcash_serialize(&mut bytes)?;
+
+            bytes.set_position(0);
+            let other_locktime = LockTime::zcash_deserialize(&mut bytes)?;
+
+            prop_assert_eq![locktime, other_locktime];
+
+
+        }
+
+
+    }
+}
diff --git a/zebra-network/src/protocol/external/types.rs b/zebra-network/src/protocol/external/types.rs
index f836dae1..0839b8de 100644
--- a/zebra-network/src/protocol/external/types.rs
+++ b/zebra-network/src/protocol/external/types.rs
@@ -81,16 +81,6 @@ mod proptest {
 
     use super::Magic;
 
-    // impl Arbitrary for Magic {
-    //     type Parameters = ();
-
-    //     fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
-    //         Magic
-    //     }
-
-    //     type Strategy = BoxedStrategy<Self>;
-    // }
-
     proptest! {
 
         #[test]