diff --git a/core/src/rpc.rs b/core/src/rpc.rs
index c7de1c404a..8a635439ef 100644
--- a/core/src/rpc.rs
+++ b/core/src/rpc.rs
@@ -578,7 +578,7 @@ impl JsonRpcRequestProcessor {
             self.check_slot_cleaned_up(&result, slot)?;
             Ok(result.ok())
         } else {
-            Ok(None)
+            Err(RpcCustomError::BlockNotAvailable { slot }.into())
         }
     }
 
@@ -650,7 +650,7 @@ impl JsonRpcRequestProcessor {
             self.check_slot_cleaned_up(&result, slot)?;
             Ok(result.ok().unwrap_or(None))
         } else {
-            Ok(None)
+            Err(RpcCustomError::BlockNotAvailable { slot }.into())
         }
     }
 
@@ -4496,7 +4496,7 @@ pub mod tests {
             slot
         );
         let res = io.handle_request_sync(&req, meta);
-        let expected = r#"{"jsonrpc":"2.0","result":null,"id":1}"#;
+        let expected = r#"{"jsonrpc":"2.0","error":{"code":-32004,"message":"Block not available for slot 12345"},"id":1}"#;
         let expected: Response =
             serde_json::from_str(&expected).expect("expected response deserialization");
         let result: Response = serde_json::from_str(&res.expect("actual response"))
diff --git a/core/src/rpc_error.rs b/core/src/rpc_error.rs
index a1ed091aad..6eea764fa4 100644
--- a/core/src/rpc_error.rs
+++ b/core/src/rpc_error.rs
@@ -5,6 +5,7 @@ const JSON_RPC_SERVER_ERROR_0: i64 = -32000;
 const JSON_RPC_SERVER_ERROR_1: i64 = -32001;
 const JSON_RPC_SERVER_ERROR_2: i64 = -32002;
 const JSON_RPC_SERVER_ERROR_3: i64 = -32003;
+const JSON_RPC_SERVER_ERROR_4: i64 = -32004;
 
 pub enum RpcCustomError {
     NonexistentClusterRoot {
@@ -19,6 +20,9 @@ pub enum RpcCustomError {
         message: String,
     },
     SendTransactionIsNotSigned,
+    BlockNotAvailable {
+        slot: Slot,
+    },
 }
 
 impl From<RpcCustomError> for Error {
@@ -56,6 +60,11 @@ impl From<RpcCustomError> for Error {
                 message: "Transaction is not signed".to_string(),
                 data: None,
             },
+            RpcCustomError::BlockNotAvailable { slot } => Self {
+                code: ErrorCode::ServerError(JSON_RPC_SERVER_ERROR_4),
+                message: format!("Block not available for slot {}", slot,),
+                data: None,
+            },
         }
     }
 }
diff --git a/docs/src/apps/jsonrpc-api.md b/docs/src/apps/jsonrpc-api.md
index 8b491e6881..5c2d35a627 100644
--- a/docs/src/apps/jsonrpc-api.md
+++ b/docs/src/apps/jsonrpc-api.md
@@ -241,7 +241,7 @@ curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "m
 
 ### getBlockTime
 
-Returns the estimated production time of a block.
+Returns the estimated production time of a confirmed block.
 
 Each validator reports their UTC time to the ledger on a regular interval by
 intermittently adding a timestamp to a Vote for a particular block. A requested
@@ -259,8 +259,8 @@ query a node that is built from genesis and retains the entire ledger.
 
 #### Results:
 
-- `<null>` - block has not yet been produced
-- `<i64>` - estimated production time, as Unix timestamp (seconds since the Unix epoch)
+* `<i64>` - estimated production time, as Unix timestamp (seconds since the Unix epoch)
+* `<null>` - timestamp is not available for this block
 
 #### Example: