diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93f3549ed1..22bb98fdc8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to the versioning scheme outlined in the [README.md](RE
 
 ## [Unreleased]
 
+### Added
+
+- Added new `ValidateRejectCode` values to the `/v3/block_proposal` endpoint
+
 ### Changed
 
 - Reduce the default `block_rejection_timeout_steps` configuration so that miners will retry faster when blocks fail to reach 70% approved or 30% rejected.
diff --git a/stackslib/src/net/api/postblock_proposal.rs b/stackslib/src/net/api/postblock_proposal.rs
index ec65278f9f..eaec726d8b 100644
--- a/stackslib/src/net/api/postblock_proposal.rs
+++ b/stackslib/src/net/api/postblock_proposal.rs
@@ -98,7 +98,10 @@ define_u8_enum![ValidateRejectCode {
     UnknownParent = 4,
     NonCanonicalTenure = 5,
     NoSuchTenure = 6,
-    InvalidTransactionReplay = 7
+    InvalidTransactionReplay = 7,
+    InvalidParentBlock = 8,
+    InvalidTimestamp = 9,
+    NetworkChainMismatch = 10
 }];
 
 pub static TOO_MANY_REQUESTS_STATUS: u16 = 429;
@@ -300,7 +303,7 @@ impl NakamotoBlockProposal {
                 "highest_header.height" => highest_header.anchored_header.height(),
             );
             return Err(BlockValidateRejectReason {
-                reason_code: ValidateRejectCode::InvalidBlock,
+                reason_code: ValidateRejectCode::InvalidParentBlock,
                 reason: "Block is not higher than the highest block in its tenure".into(),
             });
         }
@@ -423,7 +426,7 @@ impl NakamotoBlockProposal {
                 "received_mainnet" => mainnet,
             );
             return Err(BlockValidateRejectReason {
-                reason_code: ValidateRejectCode::InvalidBlock,
+                reason_code: ValidateRejectCode::NetworkChainMismatch,
                 reason: "Wrong network/chain_id".into(),
             });
         }
@@ -446,8 +449,8 @@ impl NakamotoBlockProposal {
             &self.block.header.parent_block_id,
         )?
         .ok_or_else(|| BlockValidateRejectReason {
-            reason_code: ValidateRejectCode::InvalidBlock,
-            reason: "Invalid parent block".into(),
+            reason_code: ValidateRejectCode::UnknownParent,
+            reason: "Unknown parent block".into(),
         })?;
 
         let burn_view_consensus_hash =
@@ -512,7 +515,7 @@ impl NakamotoBlockProposal {
                     "parent_block_timestamp" => parent_nakamoto_header.timestamp,
                 );
                 return Err(BlockValidateRejectReason {
-                    reason_code: ValidateRejectCode::InvalidBlock,
+                    reason_code: ValidateRejectCode::InvalidTimestamp,
                     reason: "Block timestamp is not greater than parent block".into(),
                 });
             }
@@ -525,7 +528,7 @@ impl NakamotoBlockProposal {
                 "current_time" => get_epoch_time_secs(),
             );
             return Err(BlockValidateRejectReason {
-                reason_code: ValidateRejectCode::InvalidBlock,
+                reason_code: ValidateRejectCode::InvalidTimestamp,
                 reason: "Block timestamp is too far into the future".into(),
             });
         }
diff --git a/stackslib/src/net/api/tests/postblock_proposal.rs b/stackslib/src/net/api/tests/postblock_proposal.rs
index 953ffdcdb3..f44aa54e3f 100644
--- a/stackslib/src/net/api/tests/postblock_proposal.rs
+++ b/stackslib/src/net/api/tests/postblock_proposal.rs
@@ -456,7 +456,7 @@ fn test_try_make_response() {
             reason,
             ..
         }) => {
-            assert_eq!(reason_code, ValidateRejectCode::InvalidBlock);
+            assert_eq!(reason_code, ValidateRejectCode::InvalidTimestamp);
             assert_eq!(reason, "Block timestamp is not greater than parent block");
         }
     }
@@ -469,7 +469,7 @@ fn test_try_make_response() {
             reason,
             ..
         }) => {
-            assert_eq!(reason_code, ValidateRejectCode::InvalidBlock);
+            assert_eq!(reason_code, ValidateRejectCode::InvalidTimestamp);
             assert_eq!(reason, "Block timestamp is too far into the future");
         }
     }
diff --git a/testnet/stacks-node/src/tests/nakamoto_integrations.rs b/testnet/stacks-node/src/tests/nakamoto_integrations.rs
index b399ce51b3..08b3fa5cc1 100644
--- a/testnet/stacks-node/src/tests/nakamoto_integrations.rs
+++ b/testnet/stacks-node/src/tests/nakamoto_integrations.rs
@@ -3135,7 +3135,7 @@ fn block_proposal_api_endpoint() {
                 sign(&p)
             },
             HTTP_ACCEPTED,
-            Some(Err(ValidateRejectCode::InvalidBlock)),
+            Some(Err(ValidateRejectCode::NetworkChainMismatch)),
         ),
         (
             "Invalid `miner_signature`",
diff --git a/testnet/stacks-node/src/tests/signer/v0.rs b/testnet/stacks-node/src/tests/signer/v0.rs
index 76691ad1cb..e6da7ea164 100644
--- a/testnet/stacks-node/src/tests/signer/v0.rs
+++ b/testnet/stacks-node/src/tests/signer/v0.rs
@@ -1512,7 +1512,7 @@ fn block_proposal_rejection() {
         signer_test.wait_for_validate_reject_response(short_timeout, block_signer_signature_hash_2);
     assert!(matches!(
         reject.reason_code,
-        ValidateRejectCode::InvalidBlock
+        ValidateRejectCode::UnknownParent
     ));
 
     let start_polling = Instant::now();
@@ -1542,7 +1542,7 @@ fn block_proposal_rejection() {
                     found_signer_signature_hash_2 = true;
                     assert!(matches!(
                         reason_code,
-                        RejectCode::ValidationFailed(ValidateRejectCode::InvalidBlock)
+                        RejectCode::ValidationFailed(ValidateRejectCode::UnknownParent)
                     ));
                 } else {
                     continue;