diff --git a/openmp/runtime/src/include/omp.h.var b/openmp/runtime/src/include/omp.h.var
index 0dd3a533a3650..a1488ae9d21c6 100644
--- a/openmp/runtime/src/include/omp.h.var
+++ b/openmp/runtime/src/include/omp.h.var
@@ -15,6 +15,7 @@
 #ifndef __OMP_H
 #   define __OMP_H
 
+#   include <stddef.h>
 #   include <stdlib.h>
 #   include <stdint.h>