diff --git a/include/lo2s/pipe.hpp b/include/lo2s/pipe.hpp
index db3e0a94..fbde33ae 100644
--- a/include/lo2s/pipe.hpp
+++ b/include/lo2s/pipe.hpp
@@ -53,6 +53,9 @@ class Pipe
     void close_write_fd();
 
 private:
+    constexpr static int READ_FD = 0;
+    constexpr static int WRITE_FD = 1;
+
     void fd_flags(std::size_t fd, int flags);
     void close_fd(std::size_t fd);
 
diff --git a/src/pipe.cpp b/src/pipe.cpp
index 33449ed2..93fad965 100644
--- a/src/pipe.cpp
+++ b/src/pipe.cpp
@@ -36,9 +36,6 @@ extern "C" {
 namespace lo2s
 {
 
-constexpr int READ_FD = 0;
-constexpr int WRITE_FD = 1;
-
 Pipe::Pipe()
 {
     int res = ::pipe(fds_);