diff --git a/crypto/rsa_extra/rsa_test.cc b/crypto/rsa_extra/rsa_test.cc
index 211b6903..b0a0b7e4 100644
--- a/crypto/rsa_extra/rsa_test.cc
+++ b/crypto/rsa_extra/rsa_test.cc
@@ -72,6 +72,11 @@
 #include "../internal.h"
 #include "../test/test_util.h"
 
+#if !defined(OPENSSL_NO_THREADS)
+#include <thread>
+#include <vector>
+#endif
+
 
 // kPlaintext is a sample plaintext.
 static const uint8_t kPlaintext[] = "\x54\x85\x9b\x34\x2c\x49\xea\x2a";
@@ -1042,3 +1047,73 @@ TEST(RSATest, SqrtTwo) {
   EXPECT_EQ(3072u / 2u, bits);
 }
 #endif  // !BORINGSSL_SHARED_LIBRARY
+
+#if !defined(OPENSSL_NO_THREADS)
+TEST(RSATest, Threads) {
+  bssl::UniquePtr<RSA> rsa_template(
+      RSA_private_key_from_bytes(kKey1, sizeof(kKey1) - 1));
+  ASSERT_TRUE(rsa_template);
+
+  const uint8_t kDummyHash[32] = {0};
+  uint8_t sig[256];
+  unsigned sig_len = sizeof(sig);
+  ASSERT_LE(RSA_size(rsa_template.get()), sizeof(sig));
+  EXPECT_TRUE(RSA_sign(NID_sha256, kDummyHash, sizeof(kDummyHash), sig,
+                       &sig_len, rsa_template.get()));
+
+  // RSA keys may be assembled piece-meal and then used in parallel between
+  // threads, which requires internal locking to create some derived properties.
+  bssl::UniquePtr<RSA> rsa(RSA_new());
+  rsa->n = BN_dup(rsa_template->n);
+  ASSERT_TRUE(rsa->n);
+  rsa->e = BN_dup(rsa_template->e);
+  ASSERT_TRUE(rsa->e);
+  rsa->d = BN_dup(rsa_template->d);
+  ASSERT_TRUE(rsa->d);
+  rsa->p = BN_dup(rsa_template->p);
+  ASSERT_TRUE(rsa->p);
+  rsa->q = BN_dup(rsa_template->q);
+  ASSERT_TRUE(rsa->q);
+  rsa->dmp1 = BN_dup(rsa_template->dmp1);
+  ASSERT_TRUE(rsa->dmp1);
+  rsa->dmq1 = BN_dup(rsa_template->dmq1);
+  ASSERT_TRUE(rsa->dmq1);
+  rsa->iqmp = BN_dup(rsa_template->iqmp);
+  ASSERT_TRUE(rsa->iqmp);
+
+  // Each of these operations must be safe to do concurrently on different
+  // threads.
+  auto raw_access = [&] { EXPECT_EQ(0, BN_cmp(rsa->d, rsa_template->d)); };
+  auto getter = [&] {
+    const BIGNUM *d;
+    RSA_get0_key(rsa.get(), nullptr, nullptr, &d);
+    EXPECT_EQ(0, BN_cmp(d, rsa_template->d));
+  };
+  auto sign = [&] {
+    uint8_t sig2[256];
+    unsigned sig2_len = sizeof(sig2);
+    ASSERT_LE(RSA_size(rsa.get()), sizeof(sig2));
+    EXPECT_TRUE(RSA_sign(NID_sha256, kDummyHash, sizeof(kDummyHash), sig2,
+                         &sig2_len, rsa.get()));
+    // RSASSA-PKCS1-v1_5 is deterministic.
+    EXPECT_EQ(Bytes(sig, sig_len), Bytes(sig2, sig2_len));
+  };
+  auto verify = [&] {
+    EXPECT_TRUE(RSA_verify(NID_sha256, kDummyHash, sizeof(kDummyHash), sig,
+                           sig_len, rsa.get()));
+  };
+
+  std::vector<std::thread> threads;
+  threads.emplace_back(raw_access);
+  threads.emplace_back(raw_access);
+  threads.emplace_back(getter);
+  threads.emplace_back(getter);
+  threads.emplace_back(sign);
+  threads.emplace_back(sign);
+  threads.emplace_back(verify);
+  threads.emplace_back(verify);
+  for (auto &thread : threads) {
+    thread.join();
+  }
+}
+#endif