diff --git a/simgear/sound/filters.hxx b/simgear/sound/filters.hxx
index 806c40d8..4e153c4a 100644
--- a/simgear/sound/filters.hxx
+++ b/simgear/sound/filters.hxx
@@ -23,6 +23,8 @@
 #ifndef _SIMGEAR_FREQUENCY_FILTER_HXX
 #define _SIMGEAR_FREQUENCY_FILTER_HXX
 
+#include <cstdint>
+
 namespace simgear {
 
 // Every stage is a 2nd order filter