diff --git a/package/modbus/modbus.py b/package/modbus/modbus.py
index 3cc536636..5b436d1f3 100644
--- a/package/modbus/modbus.py
+++ b/package/modbus/modbus.py
@@ -29,7 +29,9 @@ class ModBus(_modbus._ModBus):
         return ret
 
     def serializeWriteBits(self, addr: int, nb: int, src: list):
-        src = bytes(src)
+        src = bytes(len(src))
+        for i in range(len(src)):
+            src[i] = 1 if src[i] else 0
         return super().serializeWriteBits(addr, nb, src)
 
     def serializeWriteRegisters(self, addr: int, nb: int, src: list):
diff --git a/port/linux/package/pikascript/modbus.py b/port/linux/package/pikascript/modbus.py
index 3cc536636..5b436d1f3 100644
--- a/port/linux/package/pikascript/modbus.py
+++ b/port/linux/package/pikascript/modbus.py
@@ -29,7 +29,9 @@ class ModBus(_modbus._ModBus):
         return ret
 
     def serializeWriteBits(self, addr: int, nb: int, src: list):
-        src = bytes(src)
+        src = bytes(len(src))
+        for i in range(len(src)):
+            src[i] = 1 if src[i] else 0
         return super().serializeWriteBits(addr, nb, src)
 
     def serializeWriteRegisters(self, addr: int, nb: int, src: list):