diff --git a/internal/fs/const.go b/internal/fs/const.go
index dfa6ad5f0..f5f65de8e 100644
--- a/internal/fs/const.go
+++ b/internal/fs/const.go
@@ -5,12 +5,13 @@ import "syscall"
 // Flags to OpenFile wrapping those of the underlying system. Not all flags may
 // be implemented on a given system.
 const (
-	O_RDONLY int = syscall.O_RDONLY // open the file read-only.
-	O_WRONLY int = syscall.O_WRONLY // open the file write-only.
-	O_RDWR   int = syscall.O_RDWR   // open the file read-write.
-	O_APPEND int = syscall.O_APPEND // append data to the file when writing.
-	O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
-	O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist
-	O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
-	O_TRUNC  int = syscall.O_TRUNC  // if possible, truncate file when opened.
+	O_RDONLY   int = syscall.O_RDONLY   // open the file read-only.
+	O_WRONLY   int = syscall.O_WRONLY   // open the file write-only.
+	O_RDWR     int = syscall.O_RDWR     // open the file read-write.
+	O_APPEND   int = syscall.O_APPEND   // append data to the file when writing.
+	O_CREATE   int = syscall.O_CREAT    // create a new file if none exists.
+	O_EXCL     int = syscall.O_EXCL     // used with O_CREATE, file must not exist
+	O_SYNC     int = syscall.O_SYNC     // open for synchronous I/O.
+	O_TRUNC    int = syscall.O_TRUNC    // if possible, truncate file when opened.
+	O_NONBLOCK int = syscall.O_NONBLOCK // don't block open on fifos etc.
 )