1 files changed, 1 insertions, 0 deletions
diff --git a/internal/random.h b/internal/random.h
index 6498769c86..87fcc48988 100644
--- a/internal/random.h
+++ b/internal/random.h
@@ -9,6 +9,7 @@
  *             modify this file, provided that  the conditions mentioned in the
  *             file COPYING are met.  Consult the file for details.
  */
+#include <stddef.h>             /* for size_t */
 
 /* random.c */
 int ruby_fill_random_bytes(void *, size_t, int);