2 files changed, 8 insertions, 1 deletions

diff --git a/lib/libc/gen/getgrent.3 b/lib/libc/gen/getgrent.3
index be37567299c5..838e1070328b 100644
--- a/lib/libc/gen/getgrent.3
+++ b/lib/libc/gen/getgrent.3
@@ -168,9 +168,13 @@ and
 return a pointer to a group structure on success or
 .Dv NULL
 if the entry is not found or if an error occurs.
-In the latter case,
+If an error does occur,
 .Va errno
 will be set.
+Note that programs must explicitly set
+.Va errno
+to zero before calling any of these functions if they need to
+distinguish between a non-existent entry and an error.
 The functions
 .Fn getgrent_r ,
 .Fn getgrnam_r ,
diff --git a/lib/libc/gen/getgrent.c b/lib/libc/gen/getgrent.c
index d834d09fc9e6..c9b7474e78d7 100644
--- a/lib/libc/gen/getgrent.c
+++ b/lib/libc/gen/getgrent.c
@@ -307,6 +307,7 @@ getgr(int (*fn)(union key, struct group *, char *, size_t, struct group **),
 			free(grp_storage);
 			if ((grp_storage_size << 1) > GRP_STORAGE_MAX) {
 				grp_storage = NULL;
+				errno = ERANGE;
 				return (NULL);
 			}
 			grp_storage_size <<= 1;
@@ -315,6 +316,8 @@ getgr(int (*fn)(union key, struct group *, char *, size_t, struct group **),
 				return (NULL);
 		}
 	} while (res == NULL && rv == ERANGE);
+	if (rv != 0)
+		errno = rv;
 	return (res);
 }