diff --git a/substrate/client/network/light/src/light_client_requests/handler.rs b/substrate/client/network/light/src/light_client_requests/handler.rs
index 77904c7256..abf012b82f 100644
--- a/substrate/client/network/light/src/light_client_requests/handler.rs
+++ b/substrate/client/network/light/src/light_client_requests/handler.rs
@@ -173,10 +173,7 @@ where
 		let block = Decode::decode(&mut request.block.as_ref())?;
 
 		let response = match self.client.execution_proof(block, &request.method, &request.data) {
-			Ok((_, proof)) => {
-				let r = schema::v1::light::RemoteCallResponse { proof: proof.encode() };
-				Some(schema::v1::light::response::Response::RemoteCallResponse(r))
-			},
+			Ok((_, proof)) => schema::v1::light::RemoteCallResponse { proof: Some(proof.encode()) },
 			Err(e) => {
 				trace!(
 					"remote call request from {} ({} at {:?}) failed with: {}",
@@ -185,11 +182,13 @@ where
 					request.block,
 					e,
 				);
-				None
+				schema::v1::light::RemoteCallResponse { proof: None }
 			},
 		};
 
-		Ok(schema::v1::light::Response { response })
+		Ok(schema::v1::light::Response {
+			response: Some(schema::v1::light::response::Response::RemoteCallResponse(response)),
+		})
 	}
 
 	fn on_remote_read_request(
@@ -213,10 +212,7 @@ where
 
 		let response =
 			match self.client.read_proof(block, &mut request.keys.iter().map(AsRef::as_ref)) {
-				Ok(proof) => {
-					let r = schema::v1::light::RemoteReadResponse { proof: proof.encode() };
-					Some(schema::v1::light::response::Response::RemoteReadResponse(r))
-				},
+				Ok(proof) => schema::v1::light::RemoteReadResponse { proof: Some(proof.encode()) },
 				Err(error) => {
 					trace!(
 						"remote read request from {} ({} at {:?}) failed with: {}",
@@ -225,11 +221,13 @@ where
 						request.block,
 						error,
 					);
-					None
+					schema::v1::light::RemoteReadResponse { proof: None }
 				},
 			};
 
-		Ok(schema::v1::light::Response { response })
+		Ok(schema::v1::light::Response {
+			response: Some(schema::v1::light::response::Response::RemoteReadResponse(response)),
+		})
 	}
 
 	fn on_remote_read_child_request(
@@ -264,10 +262,7 @@ where
 				&mut request.keys.iter().map(AsRef::as_ref),
 			)
 		}) {
-			Ok(proof) => {
-				let r = schema::v1::light::RemoteReadResponse { proof: proof.encode() };
-				Some(schema::v1::light::response::Response::RemoteReadResponse(r))
-			},
+			Ok(proof) => schema::v1::light::RemoteReadResponse { proof: Some(proof.encode()) },
 			Err(error) => {
 				trace!(
 					"remote read child request from {} ({} {} at {:?}) failed with: {}",
@@ -277,11 +272,13 @@ where
 					request.block,
 					error,
 				);
-				None
+				schema::v1::light::RemoteReadResponse { proof: None }
 			},
 		};
 
-		Ok(schema::v1::light::Response { response })
+		Ok(schema::v1::light::Response {
+			response: Some(schema::v1::light::response::Response::RemoteReadResponse(response)),
+		})
 	}
 }
 
diff --git a/substrate/client/network/light/src/schema.rs b/substrate/client/network/light/src/schema.rs
index 09cc82cc28..1fc91659a5 100644
--- a/substrate/client/network/light/src/schema.rs
+++ b/substrate/client/network/light/src/schema.rs
@@ -23,3 +23,47 @@ pub(crate) mod v1 {
 		include!(concat!(env!("OUT_DIR"), "/api.v1.light.rs"));
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use prost::Message as _;
+
+	#[test]
+	fn empty_proof_encodes_correctly() {
+		let encoded = super::v1::light::Response {
+			response: Some(super::v1::light::response::Response::RemoteReadResponse(
+				super::v1::light::RemoteReadResponse { proof: Some(Vec::new()) },
+			)),
+		}
+		.encode_to_vec();
+
+		// Make sure that the response contains one field of number 2 and wire type 2 (message),
+		// then another field of number 2 and wire type 2 (bytes), then a length of 0.
+		assert_eq!(encoded, vec![(2 << 3) | 2, 2, (2 << 3) | 2, 0]);
+	}
+
+	#[test]
+	fn no_proof_encodes_correctly() {
+		let encoded = super::v1::light::Response {
+			response: Some(super::v1::light::response::Response::RemoteReadResponse(
+				super::v1::light::RemoteReadResponse { proof: None },
+			)),
+		}
+		.encode_to_vec();
+
+		// Make sure that the response contains one field of number 2 and wire type 2 (message).
+		assert_eq!(encoded, vec![(2 << 3) | 2, 0]);
+	}
+
+	#[test]
+	fn proof_encodes_correctly() {
+		let encoded = super::v1::light::Response {
+			response: Some(super::v1::light::response::Response::RemoteReadResponse(
+				super::v1::light::RemoteReadResponse { proof: Some(vec![1, 2, 3, 4]) },
+			)),
+		}
+		.encode_to_vec();
+
+		assert_eq!(encoded, vec![(2 << 3) | 2, 6, (2 << 3) | 2, 4, 1, 2, 3, 4]);
+	}
+}
diff --git a/substrate/client/network/light/src/schema/light.v1.proto b/substrate/client/network/light/src/schema/light.v1.proto
index 1df5466e21..a269ea73c2 100644
--- a/substrate/client/network/light/src/schema/light.v1.proto
+++ b/substrate/client/network/light/src/schema/light.v1.proto
@@ -1,17 +1,9 @@
 // Schema definition for light client messages.
 
-syntax = "proto3";
+syntax = "proto2";
 
 package api.v1.light;
 
-// A pair of arbitrary bytes.
-message Pair {
-	// The first element of the pair.
-	bytes fst = 1;
-	// The second element of the pair.
-	bytes snd = 2;
-}
-
 // Enumerate all possible light client request messages.
 message Request {
 	oneof request {
@@ -34,40 +26,42 @@ message Response {
 // Remote call request.
 message RemoteCallRequest {
 	// Block at which to perform call.
-	bytes block = 2;
+	required bytes block = 2;
 	// Method name.
-	string method = 3;
+	required string method = 3;
 	// Call data.
-	bytes data = 4;
+	required bytes data = 4;
 }
 
 // Remote call response.
 message RemoteCallResponse {
-	// Execution proof.
-	bytes proof = 2;
+	// Execution proof. If missing, indicates that the remote couldn't answer, for example because
+	// the block is pruned.
+	optional bytes proof = 2;
 }
 
 // Remote storage read request.
 message RemoteReadRequest {
 	// Block at which to perform call.
-	bytes block = 2;
+	required bytes block = 2;
 	// Storage keys.
 	repeated bytes keys = 3;
 }
 
 // Remote read response.
 message RemoteReadResponse {
-	// Read proof.
-	bytes proof = 2;
+	// Read proof. If missing, indicates that the remote couldn't answer, for example because
+	// the block is pruned.
+	optional bytes proof = 2;
 }
 
 // Remote storage read child request.
 message RemoteReadChildRequest {
 	// Block at which to perform call.
-	bytes block = 2;
+	required bytes block = 2;
 	// Child Storage key, this is relative
 	// to the child type storage location.
-	bytes storage_key = 3;
+	required bytes storage_key = 3;
 	// Storage keys.
 	repeated bytes keys = 6;
 }