diff --git a/src/platform_impl/ios/mod.rs b/src/platform_impl/ios/mod.rs
index 4ff1d3981f..b461785f6c 100644
--- a/src/platform_impl/ios/mod.rs
+++ b/src/platform_impl/ios/mod.rs
@@ -62,7 +62,8 @@
 // window size/position.
 macro_rules! assert_main_thread {
     ($($t:tt)*) => {
-        if !msg_send![class!(NSThread), isMainThread] {
+        let is_main_thread: ::objc::runtime::BOOL = msg_send!(class!(NSThread), isMainThread);
+        if is_main_thread == ::objc::runtime::NO {
             panic!($($t)*);
         }
     };
diff --git a/src/platform_impl/ios/window.rs b/src/platform_impl/ios/window.rs
index 594bcdc6ad..2a06eda217 100644
--- a/src/platform_impl/ios/window.rs
+++ b/src/platform_impl/ios/window.rs
@@ -204,7 +204,8 @@ impl Inner {
             let uiscreen = match monitor {
                 Some(Fullscreen::Exclusive(video_mode)) => {
                     let uiscreen = video_mode.video_mode.monitor.ui_screen() as id;
-                    let () = msg_send![uiscreen, setCurrentMode: video_mode.video_mode.screen_mode];
+                    let () =
+                        msg_send![uiscreen, setCurrentMode: video_mode.video_mode.screen_mode.0];
                     uiscreen
                 }
                 Some(Fullscreen::Borderless(monitor)) => monitor
diff --git a/src/platform_impl/macos/app_state.rs b/src/platform_impl/macos/app_state.rs
index 0824354b51..3c8c0535f0 100644
--- a/src/platform_impl/macos/app_state.rs
+++ b/src/platform_impl/macos/app_state.rs
@@ -19,7 +19,7 @@ use cocoa::{
 };
 use objc::{
     rc::autoreleasepool,
-    runtime::{Object, YES},
+    runtime::{Object, BOOL, NO, YES},
 };
 
 use crate::{
@@ -356,14 +356,16 @@ impl AppState {
     }
 
     pub fn queue_event(wrapper: EventWrapper) {
-        if !unsafe { msg_send![class!(NSThread), isMainThread] } {
+        let is_main_thread: BOOL = unsafe { msg_send!(class!(NSThread), isMainThread) };
+        if is_main_thread == NO {
             panic!("Event queued from different thread: {:#?}", wrapper);
         }
         HANDLER.events().push_back(wrapper);
     }
 
     pub fn queue_events(mut wrappers: VecDeque<EventWrapper>) {
-        if !unsafe { msg_send![class!(NSThread), isMainThread] } {
+        let is_main_thread: BOOL = unsafe { msg_send!(class!(NSThread), isMainThread) };
+        if is_main_thread == NO {
             panic!("Events queued from different thread: {:#?}", wrappers);
         }
         HANDLER.events().append(&mut wrappers);
@@ -400,8 +402,9 @@ impl AppState {
 
                 let dialog_open = if window_count > 1 {
                     let dialog: id = msg_send![windows, lastObject];
-                    let is_main_window: bool = msg_send![dialog, isMainWindow];
-                    msg_send![dialog, isVisible] && !is_main_window
+                    let is_main_window: BOOL = msg_send![dialog, isMainWindow];
+                    let is_visible: BOOL = msg_send![dialog, isVisible];
+                    is_visible != NO && is_main_window == NO
                 } else {
                     false
                 };
@@ -419,9 +422,9 @@ impl AppState {
                 });
 
                 if window_count > 0 {
-                    let window: id = msg_send![windows, objectAtIndex:0];
-                    let window_has_focus = msg_send![window, isKeyWindow];
-                    if !dialog_open && window_has_focus && dialog_is_closing {
+                    let window: id = msg_send![windows, firstObject];
+                    let window_has_focus: BOOL = msg_send![window, isKeyWindow];
+                    if !dialog_open && window_has_focus != NO && dialog_is_closing {
                         HANDLER.dialog_is_closing.store(false, Ordering::SeqCst);
                     }
                     if dialog_open {
diff --git a/src/platform_impl/macos/event_loop.rs b/src/platform_impl/macos/event_loop.rs
index 5ee8fbcb75..2597621349 100644
--- a/src/platform_impl/macos/event_loop.rs
+++ b/src/platform_impl/macos/event_loop.rs
@@ -12,9 +12,9 @@ use std::{
 };
 
 use cocoa::{
-    appkit::{NSApp, NSEventType::NSApplicationDefined},
-    base::{id, nil, YES},
-    foundation::NSPoint,
+    appkit::{NSApp, NSEventModifierFlags, NSEventSubtype, NSEventType::NSApplicationDefined},
+    base::{id, nil, BOOL, NO, YES},
+    foundation::{NSInteger, NSPoint, NSTimeInterval},
 };
 use objc::rc::autoreleasepool;
 
@@ -117,7 +117,8 @@ pub struct EventLoop<T: 'static> {
 impl<T> EventLoop<T> {
     pub fn new() -> Self {
         let delegate = unsafe {
-            if !msg_send![class!(NSThread), isMainThread] {
+            let is_main_thread: BOOL = msg_send!(class!(NSThread), isMainThread);
+            if is_main_thread == NO {
                 panic!("On macOS, `EventLoop` must be created on the main thread!");
             }
 
@@ -208,13 +209,13 @@ pub unsafe fn post_dummy_event(target: id) {
         event_class,
         otherEventWithType: NSApplicationDefined
         location: NSPoint::new(0.0, 0.0)
-        modifierFlags: 0
-        timestamp: 0
-        windowNumber: 0
+        modifierFlags: NSEventModifierFlags::empty()
+        timestamp: 0 as NSTimeInterval
+        windowNumber: 0 as NSInteger
         context: nil
-        subtype: 0
-        data1: 0
-        data2: 0
+        subtype: NSEventSubtype::NSWindowExposedEventType
+        data1: 0 as NSInteger
+        data2: 0 as NSInteger
     ];
     let () = msg_send![target, postEvent: dummy_event atStart: YES];
 }
diff --git a/src/platform_impl/macos/ffi.rs b/src/platform_impl/macos/ffi.rs
index 1767c7eaf9..c887cd531c 100644
--- a/src/platform_impl/macos/ffi.rs
+++ b/src/platform_impl/macos/ffi.rs
@@ -107,6 +107,7 @@ pub const kCGCursorWindowLevelKey: NSInteger = 19;
 pub const kCGNumberOfWindowLevelKeys: NSInteger = 20;
 
 #[derive(Debug, Clone, Copy)]
+#[repr(isize)]
 pub enum NSWindowLevel {
     NSNormalWindowLevel = kCGBaseWindowLevelKey as _,
     NSFloatingWindowLevel = kCGFloatingWindowLevelKey as _,
diff --git a/src/platform_impl/macos/util/async.rs b/src/platform_impl/macos/util/async.rs
index 7f8e7b8714..0c71bc8dff 100644
--- a/src/platform_impl/macos/util/async.rs
+++ b/src/platform_impl/macos/util/async.rs
@@ -10,7 +10,7 @@ use cocoa::{
 };
 use dispatch::Queue;
 use objc::rc::autoreleasepool;
-use objc::runtime::NO;
+use objc::runtime::{BOOL, NO};
 
 use crate::{
     dpi::LogicalSize,
@@ -51,7 +51,8 @@ pub unsafe fn set_style_mask_async(ns_window: id, ns_view: id, mask: NSWindowSty
     });
 }
 pub unsafe fn set_style_mask_sync(ns_window: id, ns_view: id, mask: NSWindowStyleMask) {
-    if msg_send![class!(NSThread), isMainThread] {
+    let is_main_thread: BOOL = msg_send!(class!(NSThread), isMainThread);
+    if is_main_thread != NO {
         set_style_mask(ns_window, ns_view, mask);
     } else {
         let ns_window = MainThreadSafe(ns_window);
diff --git a/src/platform_impl/macos/util/mod.rs b/src/platform_impl/macos/util/mod.rs
index 93931d2c51..6f50cbfa46 100644
--- a/src/platform_impl/macos/util/mod.rs
+++ b/src/platform_impl/macos/util/mod.rs
@@ -40,10 +40,9 @@ impl IdRef {
         IdRef(inner)
     }
 
-    #[allow(dead_code)]
     pub fn retain(inner: id) -> IdRef {
         if inner != nil {
-            let () = unsafe { msg_send![inner, retain] };
+            let _: id = unsafe { msg_send![inner, retain] };
         }
         IdRef(inner)
     }
@@ -76,10 +75,7 @@ impl Deref for IdRef {
 
 impl Clone for IdRef {
     fn clone(&self) -> IdRef {
-        if self.0 != nil {
-            let _: id = unsafe { msg_send![self.0, retain] };
-        }
-        IdRef(self.0)
+        IdRef::retain(self.0)
     }
 }
 
@@ -118,8 +114,8 @@ pub unsafe fn app_name() -> Option<id> {
 }
 
 pub unsafe fn superclass<'a>(this: &'a Object) -> &'a Class {
-    let superclass: id = msg_send![this, superclass];
-    &*(superclass as *const _)
+    let superclass: *const Class = msg_send![this, superclass];
+    &*superclass
 }
 
 pub unsafe fn create_input_context(view: id) -> IdRef {
diff --git a/src/platform_impl/macos/view.rs b/src/platform_impl/macos/view.rs
index e44fd05bb4..55271f79ea 100644
--- a/src/platform_impl/macos/view.rs
+++ b/src/platform_impl/macos/view.rs
@@ -2,7 +2,7 @@ use std::{
     boxed::Box,
     collections::VecDeque,
     os::raw::*,
-    slice, str,
+    ptr, slice, str,
     sync::{Arc, Mutex, Weak},
 };
 
@@ -314,7 +314,7 @@ extern "C" fn view_did_move_to_window(this: &Object, _sel: Sel) {
         let tracking_rect: NSInteger = msg_send![this,
             addTrackingRect:rect
             owner:this
-            userData:nil
+            userData:ptr::null_mut::<c_void>()
             assumeInside:NO
         ];
         state.tracking_rect = Some(tracking_rect);
@@ -335,7 +335,7 @@ extern "C" fn frame_did_change(this: &Object, _sel: Sel, _event: id) {
         let tracking_rect: NSInteger = msg_send![this,
             addTrackingRect:rect
             owner:this
-            userData:nil
+            userData:ptr::null_mut::<c_void>()
             assumeInside:NO
         ];
 
@@ -426,8 +426,8 @@ extern "C" fn set_marked_text(
         let marked_text_ref: &mut id = this.get_mut_ivar("markedText");
         let _: () = msg_send![(*marked_text_ref), release];
         let marked_text = NSMutableAttributedString::alloc(nil);
-        let has_attr = msg_send![string, isKindOfClass: class!(NSAttributedString)];
-        if has_attr {
+        let has_attr: BOOL = msg_send![string, isKindOfClass: class!(NSAttributedString)];
+        if has_attr != NO {
             marked_text.initWithAttributedString(string);
         } else {
             marked_text.initWithString(string);
@@ -442,7 +442,9 @@ extern "C" fn unmark_text(this: &Object, _sel: Sel) {
     unsafe {
         let marked_text: id = *this.get_ivar("markedText");
         let mutable_string = marked_text.mutableString();
-        let _: () = msg_send![mutable_string, setString:""];
+        let s: id = msg_send![class!(NSString), new];
+        let _: () = msg_send![mutable_string, setString: s];
+        let _: () = msg_send![s, release];
         let input_context: id = msg_send![this, inputContext];
         let _: () = msg_send![input_context, discardMarkedText];
     }
@@ -502,8 +504,8 @@ extern "C" fn insert_text(this: &Object, _sel: Sel, string: id, _replacement_ran
         let state_ptr: *mut c_void = *this.get_ivar("winitState");
         let state = &mut *(state_ptr as *mut ViewState);
 
-        let has_attr = msg_send![string, isKindOfClass: class!(NSAttributedString)];
-        let characters = if has_attr {
+        let has_attr: BOOL = msg_send![string, isKindOfClass: class!(NSAttributedString)];
+        let characters = if has_attr != NO {
             // This is a *mut NSAttributedString
             msg_send![string, string]
         } else {
@@ -650,7 +652,7 @@ extern "C" fn key_down(this: &Object, _sel: Sel, event: id) {
         let scancode = get_scancode(event) as u32;
         let virtual_keycode = retrieve_keycode(event);
 
-        let is_repeat = msg_send![event, isARepeat];
+        let is_repeat: BOOL = msg_send![event, isARepeat];
 
         update_potentially_stale_modifiers(state, event);
 
@@ -672,7 +674,7 @@ extern "C" fn key_down(this: &Object, _sel: Sel, event: id) {
         let pass_along = {
             AppState::queue_event(EventWrapper::StaticEvent(window_event));
             // Emit `ReceivedCharacter` for key repeats
-            if is_repeat {
+            if is_repeat != NO {
                 for character in characters.chars().filter(|c| !is_corporate_character(*c)) {
                     AppState::queue_event(EventWrapper::StaticEvent(Event::WindowEvent {
                         window_id,
@@ -914,7 +916,7 @@ fn mouse_motion(this: &Object, event: id) {
             || view_point.x > view_rect.size.width
             || view_point.y > view_rect.size.height
         {
-            let mouse_buttons_down: NSInteger = msg_send![class!(NSEvent), pressedMouseButtons];
+            let mouse_buttons_down: NSUInteger = msg_send![class!(NSEvent), pressedMouseButtons];
             if mouse_buttons_down == 0 {
                 // Point is outside of the client area (view) and no buttons are pressed
                 return;
diff --git a/src/platform_impl/macos/window.rs b/src/platform_impl/macos/window.rs
index 763439dada..f123b0936a 100644
--- a/src/platform_impl/macos/window.rs
+++ b/src/platform_impl/macos/window.rs
@@ -1,6 +1,7 @@
 use raw_window_handle::{AppKitHandle, RawWindowHandle};
 use std::{
     collections::VecDeque,
+    convert::TryInto,
     f64,
     os::raw::c_void,
     sync::{
@@ -38,7 +39,7 @@ use cocoa::{
         NSRequestUserAttentionType, NSScreen, NSView, NSWindow, NSWindowButton, NSWindowStyleMask,
     },
     base::{id, nil},
-    foundation::{NSDictionary, NSPoint, NSRect, NSSize},
+    foundation::{NSDictionary, NSPoint, NSRect, NSSize, NSUInteger},
 };
 use core_graphics::display::{CGDisplay, CGDisplayMode};
 use objc::{
@@ -332,7 +333,8 @@ impl UnownedWindow {
         pl_attribs: PlatformSpecificWindowBuilderAttributes,
     ) -> Result<(Arc<Self>, IdRef), RootOsError> {
         unsafe {
-            if !msg_send![class!(NSThread), isMainThread] {
+            let is_main_thread: BOOL = msg_send!(class!(NSThread), isMainThread);
+            if is_main_thread == NO {
                 panic!("Windows can only be created on the main thread on macOS");
             }
         }
@@ -1034,9 +1036,9 @@ impl UnownedWindow {
             let desc = NSScreen::deviceDescription(screen);
             let key = util::ns_string_id_ref("NSScreenNumber");
             let value = NSDictionary::valueForKey_(desc, *key);
-            let display_id = msg_send![value, unsignedIntegerValue];
+            let display_id: NSUInteger = msg_send![value, unsignedIntegerValue];
             RootMonitorHandle {
-                inner: MonitorHandle::new(display_id),
+                inner: MonitorHandle::new(display_id.try_into().unwrap()),
             }
         }
     }