diff --git a/crates/api-desc/CHANGELOG.md b/crates/api-desc/CHANGELOG.md
index 6aaf7be3..0c4a5d11 100644
--- a/crates/api-desc/CHANGELOG.md
+++ b/crates/api-desc/CHANGELOG.md
@@ -16,6 +16,7 @@
 
 ### Patch
 
+- Use `*const void` instead of `*const u8` for opaque data
 - Update dependencies
 - Fix lints
 
diff --git a/crates/api-desc/src/button.rs b/crates/api-desc/src/button.rs
index 4e5e7933..ac31bf9f 100644
--- a/crates/api-desc/src/button.rs
+++ b/crates/api-desc/src/button.rs
@@ -46,10 +46,10 @@ pub(crate) fn new() -> Item {
                 /// Function called on button events.
                 ///
                 /// The function takes its opaque `data` and the new button `state` as arguments.
-                handler_func: fn { data: *const u8, state: usize },
+                handler_func: fn { data: *const void, state: usize },
 
                 /// The opaque data to use when calling the handler function.
-                handler_data: *const u8,
+                handler_data: *const void,
             } -> {}
         },
         item! {
diff --git a/crates/api-desc/src/clock.rs b/crates/api-desc/src/clock.rs
index 96fbecbe..44297624 100644
--- a/crates/api-desc/src/clock.rs
+++ b/crates/api-desc/src/clock.rs
@@ -34,10 +34,10 @@ pub(crate) fn new() -> Item {
             /// Allocates a timer (initially stopped).
             fn allocate "ta" {
                 /// Function called when the timer triggers.
-                handler_func: fn { data: *const u8 },
+                handler_func: fn { data: *const void },
 
                 /// The opaque data to use when calling the handler function.
-                handler_data: *const u8,
+                handler_data: *const void,
             } -> {
                 /// Identifier for this timer.
                 id: usize,
diff --git a/crates/api-desc/src/macros.rs b/crates/api-desc/src/macros.rs
index f88baaac..4a931807 100644
--- a/crates/api-desc/src/macros.rs
+++ b/crates/api-desc/src/macros.rs
@@ -29,7 +29,7 @@ macro_rules! type_ {
     };
     (*const $($type:tt)*) => (type_!(*false $($type)*));
     (*mut $($type:tt)*) => (type_!(*true $($type)*));
-    (*$mut:tt u8) => (Type::Pointer { mutable: $mut, type_: None });
+    (*$mut:tt void) => (Type::Pointer { mutable: $mut, type_: None });
     (*$mut:tt $($type:tt)*) => {
         Type::Pointer { mutable: $mut, type_: Some(Box::new(type_!($($type)*))) }
     };
diff --git a/crates/api-desc/src/radio/ble.rs b/crates/api-desc/src/radio/ble.rs
index 1507e5f7..bb0a20a1 100644
--- a/crates/api-desc/src/radio/ble.rs
+++ b/crates/api-desc/src/radio/ble.rs
@@ -60,10 +60,10 @@ pub(crate) fn new() -> Item {
                 /// Function called on radio events.
                 ///
                 /// The function takes its opaque `data` as argument.
-                handler_func: fn { data: *mut u8 },
+                handler_func: fn { data: *const void },
 
                 /// The opaque data to use when calling the handler function.
-                handler_data: *mut u8,
+                handler_data: *const void,
             } -> {}
         },
         item! {
diff --git a/crates/api-desc/src/uart.rs b/crates/api-desc/src/uart.rs
index f6bb934c..6abe5c49 100644
--- a/crates/api-desc/src/uart.rs
+++ b/crates/api-desc/src/uart.rs
@@ -80,10 +80,10 @@ pub(crate) fn new() -> Item {
                 event: usize,
 
                 /// Function pointer of the closure to call on events.
-                handler_func: fn { data: *const u8 },
+                handler_func: fn { data: *const void },
 
                 /// Opaque data of the closure to call on events.
-                handler_data: *const u8,
+                handler_data: *const void,
             } -> {}
         },
         item! {
diff --git a/crates/api-desc/src/usb/serial.rs b/crates/api-desc/src/usb/serial.rs
index 3450be3a..af594928 100644
--- a/crates/api-desc/src/usb/serial.rs
+++ b/crates/api-desc/src/usb/serial.rs
@@ -63,8 +63,8 @@ pub(crate) fn new() -> Item {
             /// It is possible that the callback is spuriously called.
             fn register "use" {
                 event: usize,
-                handler_func: fn { data: *const u8 },
-                handler_data: *const u8,
+                handler_func: fn { data: *const void },
+                handler_data: *const void,
             } -> {}
         },
         item! {
diff --git a/crates/prelude/CHANGELOG.md b/crates/prelude/CHANGELOG.md
index 2b9233ea..fbc0d8a9 100644
--- a/crates/prelude/CHANGELOG.md
+++ b/crates/prelude/CHANGELOG.md
@@ -113,4 +113,4 @@
 
 ## 0.1.0
 
-<!-- Increment to skip CHANGELOG.md test: 17 -->
+<!-- Increment to skip CHANGELOG.md test: 18 -->
diff --git a/crates/prelude/src/radio/ble.rs b/crates/prelude/src/radio/ble.rs
index e78be502..ec31e4cc 100644
--- a/crates/prelude/src/radio/ble.rs
+++ b/crates/prelude/src/radio/ble.rs
@@ -57,7 +57,7 @@ impl<H: Handler> Listener<H> {
         let event = event as u32;
         let handler_func = Self::call;
         let handler = Box::into_raw(Box::new(handler));
-        let handler_data = handler as *mut u8;
+        let handler_data = handler as *const u8;
         unsafe { api::register(api::register::Params { event, handler_func, handler_data }) };
         Listener { handler }
     }
@@ -78,8 +78,8 @@ impl<H: Handler> Listener<H> {
         core::mem::forget(self);
     }
 
-    extern "C" fn call(data: *mut u8) {
-        let handler = unsafe { &mut *(data as *mut H) };
+    extern "C" fn call(data: *const u8) {
+        let handler = unsafe { &*(data as *const H) };
         handler.event(Event::Advertisement);
     }
 }