diff --git a/server/streamreader/process_stream.cpp b/server/streamreader/process_stream.cpp
index a7bc566d..3976f3b2 100644
--- a/server/streamreader/process_stream.cpp
+++ b/server/streamreader/process_stream.cpp
@@ -44,14 +44,14 @@ ProcessStream::ProcessStream(PcmListener* pcmListener, boost::asio::io_context&
 }
 
 
-bool ProcessStream::fileExists(const std::string& filename)
+bool ProcessStream::fileExists(const std::string& filename) const
 {
     struct stat buffer;
     return (stat(filename.c_str(), &buffer) == 0);
 }
 
 
-std::string ProcessStream::findExe(const std::string& filename)
+std::string ProcessStream::findExe(const std::string& filename) const
 {
     /// check if filename exists
     if (fileExists(filename))
diff --git a/server/streamreader/process_stream.hpp b/server/streamreader/process_stream.hpp
index d81eab16..4e726701 100644
--- a/server/streamreader/process_stream.hpp
+++ b/server/streamreader/process_stream.hpp
@@ -22,6 +22,7 @@
 #include <boost/process.hpp>
 #include <memory>
 #include <string>
+#include <vector>
 
 #include "posix_stream.hpp"
 #include "watchdog.hpp"
@@ -66,8 +67,8 @@ protected:
     virtual void onStderrMsg(const std::string& line);
     virtual void initExeAndPath(const std::string& filename);
 
-    bool fileExists(const std::string& filename);
-    std::string findExe(const std::string& filename);
+    bool fileExists(const std::string& filename) const;
+    std::string findExe(const std::string& filename) const;
 
     size_t wd_timeout_sec_;
     std::unique_ptr<Watchdog> watchdog_;