https://bugs.gentoo.org/430386
 
 src/streamtrack.cc | 1 +
 1 file changed, 1 insertion(+)

--- a/src/streamtrack.cc
+++ b/src/streamtrack.cc
@@ -34,6 +34,7 @@
 #include <sys/wait.h>
 #include <sys/stat.h>
 #include <signal.h>
+#include <unistd.h>
 
 #include <algorithm>