diff --git a/gtk2_ardour/nsmclient.cc b/gtk2_ardour/nsmclient.cc
index 7df9b7fcf3..4bcd7b43ad 100644
--- a/gtk2_ardour/nsmclient.cc
+++ b/gtk2_ardour/nsmclient.cc
@@ -29,6 +29,7 @@
 #ifndef COMPILER_MSVC
 #pragma GCC diagnostic ignored "-Wunused-parameter"
 #else
+#include <process.h>  // Needed for 'getpid()'
 
 #include <lo/lo_osc_types.h>
 #define LO_TT_IMMEDIATE lo_get_tt_immediate()