diff --git a/numpy/_core/feature_detection_locale.h b/numpy/_core/feature_detection_locale.h
index 59e78936d8d8..ccb0dc7da907 100644
--- a/numpy/_core/feature_detection_locale.h
+++ b/numpy/_core/feature_detection_locale.h
@@ -1,2 +1,5 @@
 #pragma GCC diagnostic ignored "-Wnonnull"
+#ifdef _GNU_SOURCE
+# include <bits/types/locale_t.h>
+#endif
 long double strtold_l(const char*, char**, locale_t);