diff --git a/libs/pbd3/pbd/pthread_utils.h b/libs/pbd3/pbd/pthread_utils.h
index 258604fc74..482b5b54cf 100644
--- a/libs/pbd3/pbd/pthread_utils.h
+++ b/libs/pbd3/pbd/pthread_utils.h
@@ -4,6 +4,7 @@
 #include <pthread.h>
 #include <signal.h>
 #include <string>
+#include <stdint.h>
 
 #include <sigc++/sigc++.h>