diff --git a/gpu/TODO-webgpu.h b/gpu/TODO-webgpu.h
index ea42a70d..f6a9ca84 100644
--- a/gpu/TODO-webgpu.h
+++ b/gpu/TODO-webgpu.h
@@ -1,4 +1,3 @@
-typedef void (*WGPUBufferMapCallback)(WGPUBufferMapAsyncStatus status, void * userdata);
 typedef void (*WGPUCompilationInfoCallback)(WGPUCompilationInfoRequestStatus status, WGPUCompilationInfo const * compilationInfo, void * userdata);
 typedef void (*WGPUCreateComputePipelineAsyncCallback)(WGPUCreatePipelineAsyncStatus status, WGPUComputePipeline pipeline, char const * message, void * userdata);
 typedef void (*WGPUCreateRenderPipelineAsyncCallback)(WGPUCreatePipelineAsyncStatus status, WGPURenderPipeline pipeline, char const * message, void * userdata);
diff --git a/gpu/src/buffer.zig b/gpu/src/buffer.zig
index 2d2c03da..4d6ed90c 100644
--- a/gpu/src/buffer.zig
+++ b/gpu/src/buffer.zig
@@ -3,6 +3,8 @@ const ChainedStruct = @import("types.zig").ChainedStruct;
 
 pub const Buffer = *opaque {};
 
+pub const BufferMapCallback = fn (status: BufferMapAsyncStatus, userdata: *anyopaque) callconv(.C) void;
+
 pub const BufferBindingType = enum(u32) {
     undef = 0x00000000,
     uniform = 0x00000001,