diff --git a/libs/pbd/pbd/playback_buffer.h b/libs/pbd/pbd/playback_buffer.h
index d20cea83e6..7e3a555961 100644
--- a/libs/pbd/pbd/playback_buffer.h
+++ b/libs/pbd/pbd/playback_buffer.h
@@ -45,7 +45,7 @@ public:
 		size_mask = size - 1;
 		buf = new T[size];
 
-		read_idx = 0;
+		g_atomic_int_set (&read_idx, 0);
 		reset ();
 	}