diff --git a/rpc-client-api/src/custom_error.rs b/rpc-client-api/src/custom_error.rs
index 62857b1ee55c16..2e54e8edd22e02 100644
--- a/rpc-client-api/src/custom_error.rs
+++ b/rpc-client-api/src/custom_error.rs
@@ -25,6 +25,7 @@ pub const JSON_RPC_SERVER_ERROR_BLOCK_STATUS_NOT_AVAILABLE_YET: i64 = -32014;
 pub const JSON_RPC_SERVER_ERROR_UNSUPPORTED_TRANSACTION_VERSION: i64 = -32015;
 pub const JSON_RPC_SERVER_ERROR_MIN_CONTEXT_SLOT_NOT_REACHED: i64 = -32016;
 pub const JSON_RPC_SERVER_ERROR_EPOCH_REWARDS_PERIOD_ACTIVE: i64 = -32017;
+pub const JSON_RPC_SERVER_ERROR_SLOT_NOT_EPOCH_BOUNDARY: i64 = -32018;
 
 #[derive(Error, Debug)]
 pub enum RpcCustomError {
@@ -72,6 +73,8 @@ pub enum RpcCustomError {
         current_block_height: u64,
         rewards_complete_block_height: u64,
     },
+    #[error("SlotNotEpochBoundary")]
+    SlotNotEpochBoundary { slot: Slot },
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -228,6 +231,14 @@ impl From<RpcCustomError> for Error {
                     rewards_complete_block_height,
                 })),
             },
+            RpcCustomError::SlotNotEpochBoundary { slot } => Self {
+                code: ErrorCode::ServerError(JSON_RPC_SERVER_ERROR_SLOT_NOT_EPOCH_BOUNDARY),
+                message: format!(
+                    "Rewards cannot be found because slot {slot} is not the epoch boundary. This \
+                     may be due to gap in the queried node's local ledger or long-term storage"
+                ),
+                data: None,
+            },
         }
     }
 }
diff --git a/rpc/src/rpc.rs b/rpc/src/rpc.rs
index d62a61ec81fe00..be0679c352eea1 100644
--- a/rpc/src/rpc.rs
+++ b/rpc/src/rpc.rs
@@ -633,6 +633,20 @@ impl JsonRpcRequestProcessor {
             .into());
         };
 
+        // If there is a gap in blockstore or long-term historical storage that
+        // includes the epoch boundary, the `get_blocks_with_limit()` call above
+        // will return the slot of the block at the end of that gap, not a
+        // legitimate epoch-boundary block. Therefore, verify that the parent of
+        // `epoch_boundary_block` occurred before the `first_slot_in_epoch`. If
+        // it didn't, return an error; it will be impossible to locate
+        // rewards properly.
+        if epoch_boundary_block.parent_slot >= first_slot_in_epoch {
+            return Err(RpcCustomError::SlotNotEpochBoundary {
+                slot: first_confirmed_block_in_epoch,
+            }
+            .into());
+        }
+
         // Collect rewards from first block in the epoch if partitioned epoch
         // rewards not enabled, or address is a vote account
         let mut reward_map: HashMap<String, (Reward, Slot)> = {