Index: head/contrib/netbsd-tests/lib/libc/string/t_memmem.c
===================================================================
--- head/contrib/netbsd-tests/lib/libc/string/t_memmem.c
+++ head/contrib/netbsd-tests/lib/libc/string/t_memmem.c
@@ -75,7 +75,7 @@
 ATF_TC_BODY(memmem_basic, tc)
 {
 
-#if defined(__darwin__) || defined(__FreeBSD__)
+#if defined(__darwin__)
 	expect(memmem(b2, lb2, p0, lp0) == NULL);
 	expect(memmem(b0, lb0, p0, lp0) == NULL);
 #else
Index: head/lib/libc/string/memmem.3
===================================================================
--- head/lib/libc/string/memmem.3
+++ head/lib/libc/string/memmem.3
@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 24, 2005
+.Dd May 26, 2015
 .Dt MEMMEM 3
 .Os
 .Sh NAME
@@ -51,14 +51,12 @@
 .Fa big .
 .Sh RETURN VALUES
 If
-.Fa big_len
-is smaller than
-.Fa little_len ,
-if
 .Fa little_len
-is 0, if
-.Fa big_len
-is 0 or if
+is zero
+.Fa big
+is returned (that is, an empty little is deemed to match at the beginning of
+big);
+if
 .Fa little
 occurs nowhere in
 .Fa big ,
@@ -84,3 +82,11 @@
 .Sh BUGS
 This function was broken in Linux libc up to and including version 5.0.9
 and in GNU libc prior to version 2.1.
+Prior to
+.Fx 11.0
+.Nm
+returned
+.Dv NULL
+when
+.Fa little_len
+equals 0.
Index: head/lib/libc/string/memmem.c
===================================================================
--- head/lib/libc/string/memmem.c
+++ head/lib/libc/string/memmem.c
@@ -42,9 +42,9 @@
 	const char *cl = (const char *)l;
 	const char *cs = (const char *)s;
 
-	/* we need something to compare */
-	if (l_len == 0 || s_len == 0)
-		return NULL;
+	/* empty "s" matches the beginning of "l" */
+	if (s_len == 0)
+		return (void *)cl;
 
 	/* "s" must be smaller or equal to "l" */
 	if (l_len < s_len)