diff --git a/.gitignore b/.gitignore
index 44bef90f..be47693d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -154,6 +154,7 @@ test/default/secretbox_easy2
 test/default/secretstream_xchacha20poly1305
 test/default/shorthash
 test/default/sign
+test/default/sign2
 test/default/siphashx24
 test/default/sodium_core
 test/default/sodium_utils
diff --git a/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c b/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
index a4f29a8d..00e4b5bb 100644
--- a/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
+++ b/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
@@ -2621,7 +2621,7 @@ ge25519_xmont_to_ymont(fe25519 y, const fe25519 x)
 }
 
 /* multiply by the cofactor */
-static void
+void
 ge25519_clear_cofactor(ge25519_p3 *p3)
 {
     ge25519_p1p1 p1;
diff --git a/src/libsodium/crypto_sign/ed25519/ref10/open.c b/src/libsodium/crypto_sign/ed25519/ref10/open.c
index 0ee7547c..edd129e6 100644
--- a/src/libsodium/crypto_sign/ed25519/ref10/open.c
+++ b/src/libsodium/crypto_sign/ed25519/ref10/open.c
@@ -21,8 +21,11 @@ _crypto_sign_ed25519_verify_detached(const unsigned char *sig,
     crypto_hash_sha512_state hs;
     unsigned char            h[64];
     unsigned char            rcheck[32];
+    ge25519_p3               check;
+    ge25519_p3               expected_r;
     ge25519_p3               A;
-    ge25519_p2               R;
+    ge25519_p2               sb_ah;
+    ge25519_cached           sb_ah_;
 
     ACQUIRE_FENCE;
 #ifdef ED25519_COMPAT
@@ -52,11 +55,17 @@ _crypto_sign_ed25519_verify_detached(const unsigned char *sig,
     crypto_hash_sha512_final(&hs, h);
     sc25519_reduce(h);
 
-    ge25519_double_scalarmult_vartime(&R, h, &A, sig + 32);
-    ge25519_tobytes(rcheck, &R);
+    ge25519_double_scalarmult_vartime(&sb_ah_, h, &A, sig + 32);
 
-    return crypto_verify_32(rcheck, sig) | (-(rcheck == sig)) |
-           sodium_memcmp(sig, rcheck, 32);
+
+    if (ge25519_frombytes(&expected_r, sig) != 0) {
+        return -1;
+    }
+    ge25519_p3_to_cached(&sb_ah, &sb_ah_);
+    ge25519_sub_cached(&check, &expected_r, &sb_ah);
+    ge25519_clear_cofactor(&check);
+
+    return fe25519_iszero(check.X) - 1;
 }
 
 int
diff --git a/src/libsodium/include/sodium/private/ed25519_ref10.h b/src/libsodium/include/sodium/private/ed25519_ref10.h
index fa6ca280..524c0e0e 100644
--- a/src/libsodium/include/sodium/private/ed25519_ref10.h
+++ b/src/libsodium/include/sodium/private/ed25519_ref10.h
@@ -102,6 +102,8 @@ void ge25519_double_scalarmult_vartime(ge25519_p2 *r, const unsigned char *a,
 void ge25519_scalarmult(ge25519_p3 *h, const unsigned char *a,
                         const ge25519_p3 *p);
 
+void ge25519_clear_cofactor(ge25519_p3 *p3);
+
 int ge25519_is_canonical(const unsigned char *s);
 
 int ge25519_is_on_curve(const ge25519_p3 *p);
diff --git a/test/default/Makefile.am b/test/default/Makefile.am
index f94eec8a..4ecace11 100644
--- a/test/default/Makefile.am
+++ b/test/default/Makefile.am
@@ -74,6 +74,7 @@ EXTRA_DIST = \
 	secretstream_xchacha20poly1305.exp \
 	shorthash.exp \
 	sign.exp \
+	sign2.exp \
 	siphashx24.exp \
 	sodium_core.exp \
 	sodium_utils.exp \
@@ -158,6 +159,7 @@ DISTCLEANFILES = \
 	secretstream_xchacha20poly1305.res \
 	shorthash.res \
 	sign.res \
+	sign2.res \
 	siphashx24.res \
 	sodium_core.res \
 	sodium_utils.res \
@@ -243,6 +245,7 @@ TESTS_TARGETS = \
 	secretstream_xchacha20poly1305 \
 	shorthash \
 	sign \
+	sign2 \
 	sodium_core \
 	sodium_utils \
 	sodium_version \
@@ -472,6 +475,9 @@ shorthash_LDADD           = $(TESTS_LDADD)
 sign_SOURCE               = cmptest.h sign.c
 sign_LDADD                = $(TESTS_LDADD)
 
+sign2_SOURCE              = cmptest.h sign2.c
+sign2_LDADD               = $(TESTS_LDADD)
+
 siphashx24_SOURCE         = cmptest.h siphashx24.c
 siphashx24_LDADD          = $(TESTS_LDADD)
 
diff --git a/test/default/sign2.c b/test/default/sign2.c
new file mode 100644
index 00000000..83e0a3d4
--- /dev/null
+++ b/test/default/sign2.c
@@ -0,0 +1,126 @@
+
+#define TEST_NAME "sign2"
+#include "cmptest.h"
+
+typedef struct TestData_ {
+    const char *m;
+    const char  pk[crypto_sign_PUBLICKEYBYTES * 2 + 1];
+    const char  sig[crypto_sign_BYTES * 2 + 1];
+    int         ret;
+} TestData;
+
+static TestData test_data[] = {
+    {
+        "8c93255d71dcab10e8f379c26200f3c7bd5f09d9bc3068d3ef4edeb4853022b6",
+        "c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac03fa",
+        "c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac037a00000000000000000000000000"
+        "00000000000000000000000000000000000000",
+        -1 /* WeakPublicKey */, /* 0 */
+    },
+    {
+        "9bd9f44f4dcc75bd531b56b2cd280b0bb38fc1cd6d1230e14861d861de092e79",
+        "c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac03fa",
+        "f7badec5b8abeaf699583992219b7b223f1df3fbbea919844e3f7c554a43dd43a5bb704786be79fc476f91d3f3"
+        "f89b03984d8068dcf1bb7dfc6637b45450ac04",
+        -1 /* WeakPublicKey */, /* 1 */
+    },
+    {
+        "aebf3f2601a0c8c5d39cc7d8911642f740b78168218da8471772b35f9d35b9ab",
+        "f7badec5b8abeaf699583992219b7b223f1df3fbbea919844e3f7c554a43dd43",
+        "c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac03fa8c4bd45aecaca5b24fb97bc10a"
+        "c27ac8751a7dfe1baff8b953ec9f5833ca260e",
+        -1 /* compat */, /* 2 - libsodium traditionally rejects small-order R */
+    },
+    {
+        "9bd9f44f4dcc75bd531b56b2cd280b0bb38fc1cd6d1230e14861d861de092e79",
+        "cdb267ce40c5cd45306fa5d2f29731459387dbf9eb933b7bd5aed9a765b88d4d",
+        "9046a64750444938de19f227bb80485e92b83fdb4b6506c160484c016cc1852f87909e14428a7a1d62e9f22f3d"
+        "3ad7802db02eb2e688b6c52fcd6648a98bd009",
+        0 /* acceptable */, /* 3 - mixed orders */
+    },
+    {
+        "e47d62c63f830dc7a6851a0b1f33ae4bb2f507fb6cffec4011eaccd55b53f56c",
+        "cdb267ce40c5cd45306fa5d2f29731459387dbf9eb933b7bd5aed9a765b88d4d",
+        "160a1cb0dc9c0258cd0a7d23e94d8fa878bcb1925f2c64246b2dee1796bed5125ec6bc982a269b723e0668e540"
+        "911a9a6a58921d6925e434ab10aa7940551a09",
+        0 /* acceptable */, /* 4 - cofactored verification */
+    },
+    {
+        "e47d62c63f830dc7a6851a0b1f33ae4bb2f507fb6cffec4011eaccd55b53f56c",
+        "cdb267ce40c5cd45306fa5d2f29731459387dbf9eb933b7bd5aed9a765b88d4d",
+        "21122a84e0b5fca4052f5b1235c80a537878b38f3142356b2c2384ebad4668b7e40bc836dac0f71076f9abe3a5"
+        "3f9c03c1ceeeddb658d0030494ace586687405",
+        0 /* acceptable */, /* 5 - cofactored verification */
+    },
+    {
+        "85e241a07d148b41e47d62c63f830dc7a6851a0b1f33ae4bb2f507fb6cffec40",
+        "442aad9f089ad9e14647b1ef9099a1ff4798d78589e66f28eca69c11f582a623",
+        "e96f66be976d82e60150baecff9906684aebb1ef181f67a7189ac78ea23b6c0e547f7690a0e2ddcd04d87dbc34"
+        "90dc19b3b3052f7ff0538cb68afb369ba3a514",
+        -1 /* NonCanonical */, /* 6 - S > L */
+    },
+    {
+        "85e241a07d148b41e47d62c63f830dc7a6851a0b1f33ae4bb2f507fb6cffec40",
+        "442aad9f089ad9e14647b1ef9099a1ff4798d78589e66f28eca69c11f582a623",
+        "8ce5b96c8f26d0ab6c47958c9e68b937104cd36e13c33566acd2fe8d38aa19427e71f98a4734e74f2f13f06f97"
+        "c20d58cc3f54b8bd0d272f42b695dd7e89a8c2",
+        -1 /* NonCanonical */, /* 7 - S >> L */
+    },
+    {
+        "9bedc267423725d473888631ebf45988bad3db83851ee85c85e241a07d148b41",
+        "f7badec5b8abeaf699583992219b7b223f1df3fbbea919844e3f7c554a43dd43",
+        "ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff03be9678ac102edcd92b0210bb"
+        "34d7428d12ffc5df5f37e359941266a4e35f0f",
+        -1 /* IdentityElement */, /* 8 - non-canonical R */
+    },
+    {
+        "9bedc267423725d473888631ebf45988bad3db83851ee85c85e241a07d148b41",
+        "f7badec5b8abeaf699583992219b7b223f1df3fbbea919844e3f7c554a43dd43",
+        "ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffca8c5b64cd208982aa38d49366"
+        "21a4775aa233aa0505711d8fdcfdaa943d4908",
+        -1 /* IdentityElement */, /* 9 - non-canonical R */
+    },
+    {
+        "e96b7021eb39c1a163b6da4e3093dcd3f21387da4cc4572be588fafae23c155b",
+        "ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+        "a9d55260f765261eb9b84e106f665e00b867287a761990d7135963ee0a7d59dca5bb704786be79fc476f91d3f3"
+        "f89b03984d8068dcf1bb7dfc6637b45450ac04",
+        -1 /* IdentityElement */, /* 10 - small-order A */
+    },
+    {
+        "39a591f5321bbe07fd5a23dc2f39d025d74526615746727ceefd6e82ae65c06f",
+        "ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+        "a9d55260f765261eb9b84e106f665e00b867287a761990d7135963ee0a7d59dca5bb704786be79fc476f91d3f3"
+        "f89b03984d8068dcf1bb7dfc6637b45450ac04",
+        -1 /* IdentityElement */, /* 11 - small-order A */
+    }
+};
+
+int
+main(void)
+{
+    crypto_sign_state st;
+    unsigned char     m[1024];
+    unsigned char     sig[crypto_sign_BYTES];
+    unsigned char     pk[crypto_sign_PUBLICKEYBYTES];
+    char              m_hex[1024 * 2 + 1];
+    char              sig_hex[crypto_sign_BYTES * 2 + 1];
+    char              pk_hex[crypto_sign_PUBLICKEYBYTES * 2 + 1];
+    size_t            m_len;
+    unsigned int      i;
+    int               ret;
+
+    for (i = 0U; i < (sizeof test_data) / (sizeof test_data[0]); i++) {
+        sodium_hex2bin(m, sizeof m, test_data[i].m, strlen(test_data[i].m), NULL, &m_len, NULL);
+        sodium_hex2bin(pk, sizeof pk, test_data[i].pk, strlen(test_data[i].pk), NULL, NULL, NULL);
+        sodium_hex2bin(sig, sizeof sig, test_data[i].sig, strlen(test_data[i].sig), NULL, NULL,
+                       NULL);
+        ret = crypto_sign_verify_detached(sig, m, m_len, pk);
+        if (test_data[i].ret != ret) {
+            printf("Test %u -- expected: %d found: %d\n", (unsigned int) i, test_data[i].ret, ret);
+        }
+    }
+    printf("OK\n");
+
+    return 0;
+}
diff --git a/test/default/sign2.exp b/test/default/sign2.exp
new file mode 100644
index 00000000..e69de29b