diff --git a/cyw43/src/events.rs b/cyw43/src/events.rs
index 44bfa98e9..2a78b38c3 100644
--- a/cyw43/src/events.rs
+++ b/cyw43/src/events.rs
@@ -296,10 +296,10 @@ pub struct Events {
 }
 
 impl Events {
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self {
             queue: EventQueue::new(),
-            mask: SharedEventMask::default(),
+            mask: SharedEventMask::new(),
         }
     }
 }
@@ -333,7 +333,6 @@ impl Message {
     }
 }
 
-#[derive(Default)]
 struct EventMask {
     mask: [u32; Self::WORD_COUNT],
 }
@@ -341,6 +340,12 @@ struct EventMask {
 impl EventMask {
     const WORD_COUNT: usize = ((Event::LAST as u32 + (u32::BITS - 1)) / u32::BITS) as usize;
 
+    const fn new() -> Self {
+        Self {
+            mask: [0; Self::WORD_COUNT],
+        }
+    }
+
     fn enable(&mut self, event: Event) {
         let n = event as u32;
         let word = n / u32::BITS;
@@ -366,13 +371,17 @@ impl EventMask {
     }
 }
 
-#[derive(Default)]
-
 pub struct SharedEventMask {
     mask: RefCell<EventMask>,
 }
 
 impl SharedEventMask {
+    pub const fn new() -> Self {
+        Self {
+            mask: RefCell::new(EventMask::new()),
+        }
+    }
+
     pub fn enable(&self, events: &[Event]) {
         let mut mask = self.mask.borrow_mut();
         for event in events {
@@ -398,3 +407,9 @@ impl SharedEventMask {
         mask.is_enabled(event)
     }
 }
+
+impl Default for SharedEventMask {
+    fn default() -> Self {
+        Self::new()
+    }
+}
diff --git a/cyw43/src/ioctl.rs b/cyw43/src/ioctl.rs
index af8bb695b..35135e296 100644
--- a/cyw43/src/ioctl.rs
+++ b/cyw43/src/ioctl.rs
@@ -33,8 +33,8 @@ struct Wakers {
     runner: WakerRegistration,
 }
 
-impl Default for Wakers {
-    fn default() -> Self {
+impl Wakers {
+    const fn new() -> Self {
         Self {
             control: WakerRegistration::new(),
             runner: WakerRegistration::new(),
@@ -48,10 +48,10 @@ pub struct IoctlState {
 }
 
 impl IoctlState {
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self {
             state: Cell::new(IoctlStateInner::Done { resp_len: 0 }),
-            wakers: Default::default(),
+            wakers: RefCell::new(Wakers::new()),
         }
     }
 
diff --git a/cyw43/src/lib.rs b/cyw43/src/lib.rs
index aab13d8b8..16b436e66 100644
--- a/cyw43/src/lib.rs
+++ b/cyw43/src/lib.rs
@@ -124,7 +124,7 @@ struct NetState {
 
 impl State {
     /// Create new driver state holder.
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self {
             ioctl_state: IoctlState::new(),
             net: NetState {