diff --git a/plugins/sudoers/strvec_join.c b/plugins/sudoers/strvec_join.c
index bee2e44fec..962e2c289f 100644
--- a/plugins/sudoers/strvec_join.c
+++ b/plugins/sudoers/strvec_join.c
@@ -40,7 +40,7 @@
  * char.  If non-NULL, the copy function must have strlcpy-like semantics.
  */
 char *
-strvec_join(char *const argv[], char sep, size_t (*cpy)(char *, const char *, size_t))
+strvec_join(char *const argv[], char sep, size_t (*cpy)(char * restrict, const char * restrict, size_t))
 {
     char *dst, *result = NULL;
     char *const *av;
diff --git a/plugins/sudoers/sudoers.h b/plugins/sudoers/sudoers.h
index 93c77667cb..106a1e8c2c 100644
--- a/plugins/sudoers/sudoers.h
+++ b/plugins/sudoers/sudoers.h
@@ -496,10 +496,10 @@ void canon_path_free(char *resolved);
 void canon_path_free_cache(void);
 
 /* strlcpy_unesc.c */
-size_t strlcpy_unescape(char *restrict dst, const char *restrict src, size_t size);
+size_t strlcpy_unescape(char * restrict dst, const char * restrict src, size_t size);
 
 /* strvec_join.c */
-char *strvec_join(char *const argv[], char sep, size_t (*cpy)(char *, const char *, size_t));
+char *strvec_join(char *const argv[], char sep, size_t (*cpy)(char * restrict, const char * restrict, size_t));
 
 /* unesc_str.c */
 void unescape_string(char *str);