diff --git a/tests/test_tuple_cdr.cc b/tests/test_tuple_cdr.cc
index cea800aa..da977626 100644
--- a/tests/test_tuple_cdr.cc
+++ b/tests/test_tuple_cdr.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdlib>
+#include <string>
 #include <sigc++/tuple-utils/tuple_cdr.h>
 #include <functional>
 
diff --git a/tests/test_tuple_end.cc b/tests/test_tuple_end.cc
index dcd40081..4b8de242 100644
--- a/tests/test_tuple_end.cc
+++ b/tests/test_tuple_end.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdlib>
+#include <string>
 #include <sigc++/tuple-utils/tuple_end.h>
 #include <functional>
 
diff --git a/tests/test_tuple_start.cc b/tests/test_tuple_start.cc
index 5c9e11b6..0e73fcd1 100644
--- a/tests/test_tuple_start.cc
+++ b/tests/test_tuple_start.cc
@@ -16,6 +16,7 @@
 
 #include <cassert>
 #include <cstdlib>
+#include <string>
 #include <sigc++/tuple-utils/tuple_start.h>
 #include <functional>