diff --git a/hardware_reader/applesilicon_hardware_reader.m b/hardware_reader/applesilicon_hardware_reader.m
index 038d48f..2ea9fa7 100644
--- hardware_reader/applesilicon_hardware_reader.m
+++ hardware_reader/applesilicon_hardware_reader.m
@@ -54,7 +54,7 @@ IOHIDFloat IOHIDEventGetFloatValue(IOHIDEventRef event, int32_t field);
 static dispatch_once_t once=0;
 static IOHIDEventSystemClientRef eventSystem;
 
-static void initEventSystem(){
+static void initEventSystem(void){
     dispatch_once(&once,^{
         eventSystem = IOHIDEventSystemClientCreate(kCFAllocatorDefault); // in CFBase.h = NULL
     });
diff --git a/hardware_reader/smc_reader.m b/hardware_reader/smc_reader.m
index 472379e..c09ded9 100644
--- hardware_reader/smc_reader.m
+++ hardware_reader/smc_reader.m
@@ -3,7 +3,7 @@
 
 static io_connect_t conn;
 
-kern_return_t SMCOpen()
+kern_return_t SMCOpen(void)
 {
     kern_return_t result;
     io_iterator_t iterator;
@@ -35,7 +35,7 @@ kern_return_t SMCOpen()
     return kIOReturnSuccess;
 }
 
-kern_return_t SMCClose()
+kern_return_t SMCClose(void)
 {
     return IOServiceClose(conn);
 }