diff --git a/cargo-miri-test/src/main.rs b/cargo-miri-test/src/main.rs
index 3fb265f6a7ba..6ad516710e1b 100644
--- a/cargo-miri-test/src/main.rs
+++ b/cargo-miri-test/src/main.rs
@@ -6,6 +6,6 @@ fn main() {
     let buf = &[1,2,3,4];
     let n = <BigEndian as ByteOrder>::read_u32(buf);
     assert_eq!(n, 0x01020304);
-    //println!("{:#x}", n); FIXME enable once memrchr works in miri
+    println!("{:#x}", n);
     eprintln!("standard error");
 }
diff --git a/cargo-miri-test/stdout.ref b/cargo-miri-test/stdout.ref
index e69de29bb2d1..6710f307cb26 100644
--- a/cargo-miri-test/stdout.ref
+++ b/cargo-miri-test/stdout.ref
@@ -0,0 +1 @@
+0x01020304
diff --git a/tests/run-pass-fullmir/memchr.rs b/tests/run-pass-fullmir/memchr.rs
new file mode 100644
index 000000000000..36eb85dcf7e8
--- /dev/null
+++ b/tests/run-pass-fullmir/memchr.rs
@@ -0,0 +1,90 @@
+#![feature(slice_internals)]
+
+extern crate core;
+use core::slice::memchr::{memchr, memrchr};
+
+// test fallback implementations on all platforms
+fn matches_one() {
+    assert_eq!(Some(0), memchr(b'a', b"a"));
+}
+
+fn matches_begin() {
+    assert_eq!(Some(0), memchr(b'a', b"aaaa"));
+}
+
+fn matches_end() {
+    assert_eq!(Some(4), memchr(b'z', b"aaaaz"));
+}
+
+fn matches_nul() {
+    assert_eq!(Some(4), memchr(b'\x00', b"aaaa\x00"));
+}
+
+fn matches_past_nul() {
+    assert_eq!(Some(5), memchr(b'z', b"aaaa\x00z"));
+}
+
+fn no_match_empty() {
+    assert_eq!(None, memchr(b'a', b""));
+}
+
+fn no_match() {
+    assert_eq!(None, memchr(b'a', b"xyz"));
+}
+
+fn matches_one_reversed() {
+    assert_eq!(Some(0), memrchr(b'a', b"a"));
+}
+
+fn matches_begin_reversed() {
+    assert_eq!(Some(3), memrchr(b'a', b"aaaa"));
+}
+
+fn matches_end_reversed() {
+    assert_eq!(Some(0), memrchr(b'z', b"zaaaa"));
+}
+
+fn matches_nul_reversed() {
+    assert_eq!(Some(4), memrchr(b'\x00', b"aaaa\x00"));
+}
+
+fn matches_past_nul_reversed() {
+    assert_eq!(Some(0), memrchr(b'z', b"z\x00aaaa"));
+}
+
+fn no_match_empty_reversed() {
+    assert_eq!(None, memrchr(b'a', b""));
+}
+
+fn no_match_reversed() {
+    assert_eq!(None, memrchr(b'a', b"xyz"));
+}
+
+fn each_alignment_reversed() {
+    let mut data = [1u8; 64];
+    let needle = 2;
+    let pos = 40;
+    data[pos] = needle;
+    for start in 0..16 {
+        assert_eq!(Some(pos - start), memrchr(needle, &data[start..]));
+    }
+}
+
+fn main() {
+    matches_one();
+    matches_begin();
+    matches_end();
+    matches_nul();
+    matches_past_nul();
+    no_match_empty();
+    no_match();
+
+    matches_one_reversed();
+    matches_begin_reversed();
+    matches_end_reversed();
+    matches_nul_reversed();
+    matches_past_nul_reversed();
+    no_match_empty_reversed();
+    no_match_reversed();
+    each_alignment_reversed();
+}