diff --git a/realize/utils_unix.go b/realize/utils_unix.go
index a6ed554..4d8339b 100644
--- a/realize/utils_unix.go
+++ b/realize/utils_unix.go
@@ -1,3 +1,5 @@
+// +build !windows
+
 package realize
 
 import "strings"
diff --git a/realize/utils_windows.go b/realize/utils_windows.go
index 51d5fce..8253a9d 100644
--- a/realize/utils_windows.go
+++ b/realize/utils_windows.go
@@ -1,3 +1,5 @@
+// +build windows
+
 package realize
 
 import "syscall"