diff --git a/include/RFID.h b/include/RFID.h
index c134fa4..168eca4 100644
--- a/include/RFID.h
+++ b/include/RFID.h
@@ -98,6 +98,16 @@ private:
 	 * @return True if read succeeded, false otherwise.
 	 */
 	bool readBlock(MFRC522Constants::Uid &tagUid, byte blockAddr);
+
+	/**
+	 * Write data to tagUid at blockAddr and return if the write succeeded or not.
+	 * The tag needs to be already woken up.
+	 * @param tagUid Uid of the tag to write to.
+	 * @param blockAddr Address of the block to write to.
+	 * @param data Byte to write.
+	 * @return True if write succeeded, false otherwise.
+	 */
+	bool writeBlock(MFRC522Constants::Uid &tagUid, byte blockAddr, uint8_t data);
 };
 
 #endif //JIN_BARBAPAPA_RFID_H
diff --git a/src/RFID.cpp b/src/RFID.cpp
index fd40870..7df626d 100644
--- a/src/RFID.cpp
+++ b/src/RFID.cpp
@@ -116,3 +116,26 @@ bool RFID::readBlock(MFRC522Constants::Uid &uidToRead, byte blockAddr) {
 	mfrc.PICC_HaltA();
 	return status == MFRC522Constants::STATUS_OK;
 }
+
+bool RFID::writeBlock(MFRC522Constants::Uid &uidToRead, byte blockAddr, uint8_t data) {
+	if (mfrc.PCD_Authenticate(
+			MFRC522Constants::PICC_Command::PICC_CMD_MF_AUTH_KEY_A,
+			blockAddr, (&defaultKey),&uidToRead)!= MFRC522Constants::STATUS_OK) {
+		Serial.println("writeBlock: Failed to authenticate");
+		mfrc.PICC_HaltA();
+		return false;
+	}
+
+	byte size = sizeof(comData);
+	for (byte& bufferByte: comData)
+		bufferByte = 0;
+
+	*comData = data;
+
+	MFRC522::StatusCode status = mfrc.MIFARE_Write(blockAddr, comData, size);
+	// Needed otherwise no new communications can happen.
+	mfrc.PCD_StopCrypto1();
+	// No need to keep the tag active.
+	mfrc.PICC_HaltA();
+	return status == MFRC522Constants::STATUS_OK;
+}