diff --git a/deno_webgpu/buffer.rs b/deno_webgpu/buffer.rs
index 3cb9fdf83..9a2ebb003 100644
--- a/deno_webgpu/buffer.rs
+++ b/deno_webgpu/buffer.rs
@@ -98,7 +98,8 @@ pub async fn op_webgpu_buffer_get_map_async(
         // TODO(lucacasonato): error handling
         let maybe_err = gfx_select!(buffer => instance.buffer_map_async(
             buffer,
-            offset..(offset + size),
+            offset,
+            Some(size),
             wgpu_core::resource::BufferMapOperation {
                 host: match mode {
                     1 => wgpu_core::device::HostMap::Read,
diff --git a/player/tests/test.rs b/player/tests/test.rs
index e38de1cea..c04622b42 100644
--- a/player/tests/test.rs
+++ b/player/tests/test.rs
@@ -131,7 +131,8 @@ impl Test<'_> {
             let buffer = wgc::id::Id::zip(expect.buffer.index, expect.buffer.epoch, backend);
             wgc::gfx_select!(device_id => global.buffer_map_async(
                 buffer,
-                expect.offset .. expect.offset+expect.data.len() as wgt::BufferAddress,
+                expect.offset,
+                Some(expect.data.len() as u64),
                 wgc::resource::BufferMapOperation {
                     host: wgc::device::HostMap::Read,
                     callback: Some(wgc::resource::BufferMapCallback::from_rust(
diff --git a/wgpu-core/src/device/global.rs b/wgpu-core/src/device/global.rs
index 64fd6d4de..e5c4e733b 100644
--- a/wgpu-core/src/device/global.rs
+++ b/wgpu-core/src/device/global.rs
@@ -26,9 +26,7 @@ use wgt::{BufferAddress, TextureFormat};
 
 use std::{
     borrow::Cow,
-    iter,
-    ops::Range,
-    ptr,
+    iter, ptr,
     sync::{atomic::Ordering, Arc},
 };
 
@@ -2336,15 +2334,18 @@ impl Global {
     pub fn buffer_map_async<A: HalApi>(
         &self,
         buffer_id: id::BufferId,
-        range: Range<BufferAddress>,
+        offset: BufferAddress,
+        size: Option<BufferAddress>,
         op: BufferMapOperation,
     ) -> BufferAccessResult {
-        api_log!("Buffer::map_async {buffer_id:?} range {range:?} op: {op:?}");
+        api_log!("Buffer::map_async {buffer_id:?} offset {offset:?} size {size:?} op: {op:?}");
 
         // User callbacks must not be called while holding buffer_map_async_inner's locks, so we
         // defer the error callback if it needs to be called immediately (typically when running
         // into errors).
-        if let Err((mut operation, err)) = self.buffer_map_async_inner::<A>(buffer_id, range, op) {
+        if let Err((mut operation, err)) =
+            self.buffer_map_async_inner::<A>(buffer_id, offset, size, op)
+        {
             if let Some(callback) = operation.callback.take() {
                 callback.call(Err(err.clone()));
             }
@@ -2360,7 +2361,8 @@ impl Global {
     fn buffer_map_async_inner<A: HalApi>(
         &self,
         buffer_id: id::BufferId,
-        range: Range<BufferAddress>,
+        offset: BufferAddress,
+        size: Option<BufferAddress>,
         op: BufferMapOperation,
     ) -> Result<(), (BufferMapOperation, BufferAccessError)> {
         profiling::scope!("Buffer::map_async");
@@ -2372,22 +2374,43 @@ impl Global {
             HostMap::Write => (wgt::BufferUsages::MAP_WRITE, hal::BufferUses::MAP_WRITE),
         };
 
-        if range.start % wgt::MAP_ALIGNMENT != 0 || range.end % wgt::COPY_BUFFER_ALIGNMENT != 0 {
-            return Err((op, BufferAccessError::UnalignedRange));
-        }
-
         let buffer = {
-            let buffer = hub
-                .buffers
-                .get(buffer_id)
-                .map_err(|_| BufferAccessError::Invalid);
+            let buffer = hub.buffers.get(buffer_id);
 
             let buffer = match buffer {
                 Ok(b) => b,
-                Err(e) => {
-                    return Err((op, e));
+                Err(_) => {
+                    return Err((op, BufferAccessError::Invalid));
                 }
             };
+            {
+                let snatch_guard = buffer.device.snatchable_lock.read();
+                if buffer.is_destroyed(&snatch_guard) {
+                    return Err((op, BufferAccessError::Destroyed));
+                }
+            }
+
+            let range_size = if let Some(size) = size {
+                size
+            } else if offset > buffer.size {
+                0
+            } else {
+                buffer.size - offset
+            };
+
+            if offset % wgt::MAP_ALIGNMENT != 0 {
+                return Err((op, BufferAccessError::UnalignedOffset { offset }));
+            }
+            if range_size % wgt::COPY_BUFFER_ALIGNMENT != 0 {
+                return Err((op, BufferAccessError::UnalignedRangeSize { range_size }));
+            }
+
+            let range = offset..(offset + range_size);
+
+            if range.start % wgt::MAP_ALIGNMENT != 0 || range.end % wgt::COPY_BUFFER_ALIGNMENT != 0
+            {
+                return Err((op, BufferAccessError::UnalignedRange));
+            }
 
             let device = &buffer.device;
             if !device.is_valid() {
@@ -2417,11 +2440,6 @@ impl Global {
                 ));
             }
 
-            let snatch_guard = device.snatchable_lock.read();
-            if buffer.is_destroyed(&snatch_guard) {
-                return Err((op, BufferAccessError::Destroyed));
-            }
-
             {
                 let map_state = &mut *buffer.map_state.lock();
                 *map_state = match *map_state {
@@ -2442,6 +2460,8 @@ impl Global {
                 };
             }
 
+            let snatch_guard = buffer.device.snatchable_lock.read();
+
             {
                 let mut trackers = buffer.device.as_ref().trackers.lock();
                 trackers.buffers.set_single(&buffer, internal_use);
diff --git a/wgpu/src/backend/wgpu_core.rs b/wgpu/src/backend/wgpu_core.rs
index 3901e7d44..b43291e79 100644
--- a/wgpu/src/backend/wgpu_core.rs
+++ b/wgpu/src/backend/wgpu_core.rs
@@ -1453,7 +1453,8 @@ impl crate::Context for ContextWgpuCore {
             ))),
         };
 
-        match wgc::gfx_select!(buffer => self.0.buffer_map_async(*buffer, range, operation)) {
+        match wgc::gfx_select!(buffer => self.0.buffer_map_async(*buffer, range.start, Some(range.end-range.start), operation))
+        {
             Ok(()) => (),
             Err(cause) => {
                 self.handle_error_nolabel(&buffer_data.error_sink, cause, "Buffer::map_async")