diff --git a/libs/ardour/test/testrunner.cc b/libs/ardour/test/testrunner.cc
index fa4484fa25..2f932c62da 100644
--- a/libs/ardour/test/testrunner.cc
+++ b/libs/ardour/test/testrunner.cc
@@ -1,4 +1,5 @@
 #include <getopt.h>
+#include <glibmm/thread.h>
 
 #include <cppunit/CompilerOutputter.h>
 #include <cppunit/extensions/TestFactoryRegistry.h>
diff --git a/libs/audiographer/tests/test_runner.cc b/libs/audiographer/tests/test_runner.cc
index 756a45fd42..d378b5e4cb 100644
--- a/libs/audiographer/tests/test_runner.cc
+++ b/libs/audiographer/tests/test_runner.cc
@@ -1,5 +1,6 @@
 #include <cppunit/extensions/TestFactoryRegistry.h>
 #include <cppunit/ui/text/TestRunner.h>
+#include <glibmm/thread.h>
 
 int main()
 {
diff --git a/libs/pbd/test/signals_test.cc b/libs/pbd/test/signals_test.cc
index 4b425590ad..2cfe5519c0 100644
--- a/libs/pbd/test/signals_test.cc
+++ b/libs/pbd/test/signals_test.cc
@@ -1,3 +1,5 @@
+#include <glibmm/thread.h>
+
 #include "signals_test.h"
 #include "pbd/signals.h"