diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiCharacteristic.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiCharacteristic.java
index 70a06ad35..0ce491bb4 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiCharacteristic.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiCharacteristic.java
@@ -258,7 +258,7 @@ public class XiaomiCharacteristic {
             buf.putShort((short) 0);
             buf.put((byte) 0);
             buf.put((byte) (isEncrypted ? 1 : 0));
-            buf.putShort((short) Math.round(currentSending.length / 247.0));
+            buf.putShort((short) Math.max(1,Math.round(currentSending.length / 247.0)));
 
             final TransactionBuilder builder = mSupport.createTransactionBuilder("send chunked start");
             builder.write(bluetoothGattCharacteristic, buf.array());
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiPlaintextSupport.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiPlaintextSupport.java
index ff668849a..422f3ec28 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiPlaintextSupport.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/xiaomi/XiaomiPlaintextSupport.java
@@ -67,12 +67,12 @@ public class XiaomiPlaintextSupport extends XiaomiSupport {
         this.characteristicCommandRead.setEncrypted(false);
         this.characteristicCommandRead.setHandler(this::handleCommandBytes);
         this.characteristicCommandWrite = new XiaomiCharacteristic(this, btCharacteristicCommandWrite, authService);
-        this.characteristicCommandRead.setEncrypted(false);
+        this.characteristicCommandWrite.setEncrypted(false);
         this.characteristicActivityData = new XiaomiCharacteristic(this, btCharacteristicActivityData, authService);
         this.characteristicActivityData.setHandler(healthService.getActivityFetcher()::addChunk);
-        this.characteristicCommandRead.setEncrypted(false);
+        this.characteristicActivityData.setEncrypted(false);
         this.characteristicDataUpload = new XiaomiCharacteristic(this, btCharacteristicDataUpload, authService);
-        this.characteristicCommandRead.setEncrypted(false);
+        this.characteristicDataUpload.setEncrypted(false);
 
         // FIXME why is this needed?
         getDevice().setFirmwareVersion("...");