diff --git a/stepmania/src/arch/Threads/Threads_Pthreads.h b/stepmania/src/arch/Threads/Threads_Pthreads.h
index d171473118..bb29500b92 100644
--- a/stepmania/src/arch/Threads/Threads_Pthreads.h
+++ b/stepmania/src/arch/Threads/Threads_Pthreads.h
@@ -7,6 +7,7 @@
 #define PID_BASED_THREADS
 #endif
 
+#include <pthread.h>
 #include <semaphore.h>
 
 class ThreadImpl_Pthreads: public ThreadImpl