diff --git a/zebra-chain/src/block.rs b/zebra-chain/src/block.rs
index 15ee3c202..e2058fc46 100644
--- a/zebra-chain/src/block.rs
+++ b/zebra-chain/src/block.rs
@@ -145,6 +145,8 @@ impl ZcashSerialize for BlockHeader {
         self.previous_block_hash.zcash_serialize(&mut writer)?;
         writer.write_all(&self.merkle_root_hash.0[..])?;
         writer.write_all(&self.final_sapling_root_hash.0[..])?;
+        // this is a truncating cast, rather than a saturating cast
+        // but u32 times are valid until 2106
         writer.write_u32::<LittleEndian>(self.time.timestamp() as u32)?;
         writer.write_u32::<LittleEndian>(self.bits)?;
         writer.write_all(&self.nonce[..])?;
@@ -190,6 +192,7 @@ impl ZcashDeserialize for BlockHeader {
             previous_block_hash: BlockHeaderHash::zcash_deserialize(&mut reader)?,
             merkle_root_hash: MerkleTreeRootHash(reader.read_32_bytes()?),
             final_sapling_root_hash: SaplingNoteTreeRootHash(reader.read_32_bytes()?),
+            // This can't panic, because all u32 values are valid `Utc.timestamp`s
             time: Utc.timestamp(reader.read_u32::<LittleEndian>()? as i64, 0),
             bits: reader.read_u32::<LittleEndian>()?,
             nonce: reader.read_32_bytes()?,
diff --git a/zebra-chain/src/block/tests.rs b/zebra-chain/src/block/tests.rs
index 7c633b9f1..98c2fd776 100644
--- a/zebra-chain/src/block/tests.rs
+++ b/zebra-chain/src/block/tests.rs
@@ -16,11 +16,13 @@ impl Arbitrary for BlockHeader {
 
     fn arbitrary_with(_args: ()) -> Self::Strategy {
         (
-            (4u32..2_147_483_647u32),
+            // version is interpreted as i32 in the spec, so we are limited to i32::MAX here
+            (4u32..(i32::MAX as u32)),
             any::<BlockHeaderHash>(),
             any::<MerkleTreeRootHash>(),
             any::<SaplingNoteTreeRootHash>(),
-            (0i64..4_294_967_296i64),
+            // time is interpreted as u32 in the spec, but rust timestamps are i64
+            (0i64..(u32::MAX as i64)),
             any::<u32>(),
             any::<[u8; 32]>(),
             any::<EquihashSolution>(),