diff --git a/Project.toml b/Project.toml
index ef0a59e..d059e87 100644
--- a/Project.toml
+++ b/Project.toml
@@ -14,10 +14,12 @@ StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 [weakdeps]
 AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
+Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
 
 [extensions]
 NNopAMDGPUExt = "AMDGPU"
 NNopCUDAExt = "CUDA"
+NNopMetalExt = "Metal"
 
 [compat]
 AMDGPU = "1.2.5, 2"
diff --git a/ext/NNopMetalExt.jl b/ext/NNopMetalExt.jl
new file mode 100644
index 0000000..28ca1e7
--- /dev/null
+++ b/ext/NNopMetalExt.jl
@@ -0,0 +1,11 @@
+module NNopMetalExt
+
+using Metal
+using NNop
+
+function NNop._shared_memory(::MetalBackend, device_id::Integer)
+    dev = Metal.devices()[device_id]
+    return UInt64(dev.maxThreadgroupMemoryLength)
+end
+
+end