diff --git a/src/CUDAKernels.jl b/src/CUDAKernels.jl
index c3d014b351..ee8f904bd7 100644
--- a/src/CUDAKernels.jl
+++ b/src/CUDAKernels.jl
@@ -57,14 +57,17 @@ end
 ## device operations
 
 function KA.ndevices(::CUDABackend)
-    return ndevices()
+    return Int(ndevices())
 end
 
-function KA.device(::CUDABackend)
+function KA.device(::CUDABackend)::Int
     deviceid(CUDA.active_state().device) + 1
 end
 
-function KA.device!(::CUDABackend, id::Int32)
+function KA.device!(backend::CUDABackend, id::Int)
+    if !(0 < id <= KA.ndevices(backend))
+        throw(ArgumentError("Device id $id out of bounds."))
+    end
     device!(id - 1)
 end