diff --git a/include/wordexp.h b/include/wordexp.h
index a6f0213db250..aee7caf32f34 100644
--- a/include/wordexp.h
+++ b/include/wordexp.h
@@ -50,7 +50,7 @@ typedef struct {
  */
 #define	WRDE_APPEND	0x1		/* append to previously generated */
 #define	WRDE_DOOFS	0x2		/* we_offs member is valid */
-#define	WRDE_NOCMD	0x4
+#define	WRDE_NOCMD	0x4		/* disallow command substitution */
 #define	WRDE_REUSE	0x8		/* reuse wordexp_t */
 #define	WRDE_SHOWERR	0x10		/* don't redirect stderr to /dev/null */
 #define	WRDE_UNDEF	0x20		/* disallow undefined shell vars */