diff --git a/src/util/subprocess.h b/src/util/subprocess.h
index b4a99f08990..a0d52b1c19b 100644
--- a/src/util/subprocess.h
+++ b/src/util/subprocess.h
@@ -738,6 +738,7 @@ private:
   Popen* popen_ = nullptr;
 };
 
+#ifndef __USING_WINDOWS__
 /*!
  * A helper class to Popen.
  * This takes care of all the fork-exec logic
@@ -759,6 +760,7 @@ private:
   Popen* parent_ = nullptr;
   int err_wr_pipe_ = -1;
 };
+#endif
 
 // Fwd Decl.
 class Streams;
@@ -930,7 +932,9 @@ class Popen
 {
 public:
   friend struct detail::ArgumentDeducer;
+#ifndef __USING_WINDOWS__
   friend class detail::Child;
+#endif
 
   template <typename... Args>
   Popen(std::initializer_list<const char*> cmd_args, Args&& ...args)
@@ -1009,6 +1013,9 @@ private:
 #ifdef __USING_WINDOWS__
   HANDLE process_handle_;
   std::future<void> cleanup_future_;
+#else
+  // Pid of the child process
+  int child_pid_ = -1;
 #endif
 
   std::string exe_name_;
@@ -1017,9 +1024,6 @@ private:
   std::vector<std::string> vargs_;
   std::vector<char*> cargv_;
 
-  // Pid of the child process
-  int child_pid_ = -1;
-
   int retcode_ = -1;
 };
 
@@ -1258,8 +1262,8 @@ namespace detail {
   }
 
 
-  inline void Child::execute_child() {
 #ifndef __USING_WINDOWS__
+  inline void Child::execute_child() {
     int sys_ret = -1;
     auto& stream = parent_->stream_;
 
@@ -1319,8 +1323,8 @@ namespace detail {
     // Calling application would not get this
     // exit failure
     _exit (EXIT_FAILURE);
-#endif
   }
+#endif
 
 
   inline void Streams::setup_comm_channels()