diff --git a/uptime_darwin.go b/uptime_darwin.go
new file mode 100644
index 0000000..fc53f49
--- /dev/null
+++ b/uptime_darwin.go
@@ -0,0 +1,12 @@
+//go:build darwin
+
+package themis
+
+import (
+	"time"
+)
+
+// Uptime returns the time elapsed since the start of the current process ID.
+func Uptime() (time.Duration, error) {
+	panic("not implemented")
+}
diff --git a/uptime.go b/uptime_linux.go
similarity index 96%
rename from uptime.go
rename to uptime_linux.go
index 03d53e1..11f8f3c 100644
--- a/uptime.go
+++ b/uptime_linux.go
@@ -1,3 +1,5 @@
+//go:build linux
+
 package themis
 
 import (