diff --git a/client.cpp b/client.cpp
index c054e659..e55f547f 100644
--- a/client.cpp
+++ b/client.cpp
@@ -14,6 +14,7 @@
 #include <algorithm>
 #include <thread> 
 #include <mutex>
+#include <condition_variable>
 
 //44100 / 20 = 2205
 const size_t size(4*2205);