diff --git a/unix/affinity_linux.go b/unix/affinity_linux.go
index d81fbb5b..72afe333 100644
--- a/unix/affinity_linux.go
+++ b/unix/affinity_linux.go
@@ -16,7 +16,7 @@ const cpuSetSize = _CPU_SETSIZE / _NCPUBITS
 type CPUSet [cpuSetSize]cpuMask
 
 func schedAffinity(trap uintptr, pid int, set *CPUSet) error {
-	_, _, e := RawSyscall(trap, uintptr(pid), uintptr(unsafe.Sizeof(set)), uintptr(unsafe.Pointer(set)))
+	_, _, e := RawSyscall(trap, uintptr(pid), uintptr(unsafe.Sizeof(*set)), uintptr(unsafe.Pointer(set)))
 	if e != 0 {
 		return errnoErr(e)
 	}