diff --git a/subprocess.hpp b/subprocess.hpp
index 112038a..d5d491a 100755
--- a/subprocess.hpp
+++ b/subprocess.hpp
@@ -146,12 +146,13 @@ public:
 
 namespace util
 {
-  template <typename R> bool is_ready(std::shared_future<R> const &f)
+  template <typename R>
+  inline bool is_ready(std::shared_future<R> const &f)
   {
     return f.wait_for(std::chrono::seconds(0)) == std::future_status::ready;
   }
 
-  void quote_argument(const std::wstring &argument, std::wstring &command_line,
+  inline void quote_argument(const std::wstring &argument, std::wstring &command_line,
                       bool force)
   {
     //