diff --git a/include/os.h b/include/os.h
index ffa5f3923..263374185 100644
--- a/include/os.h
+++ b/include/os.h
@@ -74,6 +74,8 @@ typedef struct _NewClientRec *NewClientPtr;
 
 #define xstrdup(s) Xstrdup(s)
 #define xnfstrdup(s) XNFstrdup(s)
+
+#define xallocarray(num, size) reallocarray(NULL, (num), (size))
 #endif
 
 #include <stdio.h>