diff --git a/src/tests/allocs-by-size.c b/src/tests/allocs-by-size.c
index f0d3f241..666113a3 100644
--- a/src/tests/allocs-by-size.c
+++ b/src/tests/allocs-by-size.c
@@ -21,6 +21,7 @@
 #include "config.h"
 
 #include <glib/gi18n.h>
+#include <locale.h>
 #include <stddef.h>
 #include <rax.h>
 #include <sysprof.h>
diff --git a/src/tests/memory-stack-stash.c b/src/tests/memory-stack-stash.c
index 9d6859d1..7b6675c6 100644
--- a/src/tests/memory-stack-stash.c
+++ b/src/tests/memory-stack-stash.c
@@ -21,6 +21,7 @@
 #include "config.h"
 
 #include <glib/gi18n.h>
+#include <locale.h>
 #include <stddef.h>
 #include <rax.h>
 #include <sysprof.h>