diff --git a/crypto/err/pkcs8.errordata b/crypto/err/pkcs8.errordata
index 8b51274..225b34c 100644
--- a/crypto/err/pkcs8.errordata
+++ b/crypto/err/pkcs8.errordata
@@ -8,6 +8,7 @@
 PKCS8,106,ENCRYPT_ERROR
 PKCS8,107,ERROR_SETTING_CIPHER_PARAMS
 PKCS8,108,INCORRECT_PASSWORD
+PKCS8,131,INVALID_CHARACTERS
 PKCS8,109,KEYGEN_FAILURE
 PKCS8,110,KEY_GEN_ERROR
 PKCS8,111,METHOD_NOT_SUPPORTED
diff --git a/crypto/pkcs8/pkcs12_test.cc b/crypto/pkcs8/pkcs12_test.cc
index 66d0397..2190e37 100644
--- a/crypto/pkcs8/pkcs12_test.cc
+++ b/crypto/pkcs8/pkcs12_test.cc
@@ -20,6 +20,7 @@
 #include <openssl/err.h>
 #include <openssl/evp.h>
 #include <openssl/pkcs8.h>
+#include <openssl/span.h>
 #include <openssl/stack.h>
 #include <openssl/x509.h>
 
@@ -899,22 +900,110 @@
 
 static const char kPassword[] = "foo";
 
-static void TestImpl(const char *name, const uint8_t *der, size_t der_len) {
+// Generated with
+//   openssl pkcs12 -export -inkey ecdsa_p256_key.pem -in ecdsa_p256_cert.pem -password pass:"Hello, 世界"
+static const uint8_t kUnicode[] = {
+    0x30, 0x82, 0x03, 0xd2, 0x02, 0x01, 0x03, 0x30, 0x82, 0x03, 0x98, 0x06,
+    0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x01, 0xa0, 0x82,
+    0x03, 0x89, 0x04, 0x82, 0x03, 0x85, 0x30, 0x82, 0x03, 0x81, 0x30, 0x82,
+    0x02, 0x77, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07,
+    0x06, 0xa0, 0x82, 0x02, 0x68, 0x30, 0x82, 0x02, 0x64, 0x02, 0x01, 0x00,
+    0x30, 0x82, 0x02, 0x5d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
+    0x01, 0x07, 0x01, 0x30, 0x1c, 0x06, 0x0a, 0x2a, 0x86, 0x48, 0x86, 0xf7,
+    0x0d, 0x01, 0x0c, 0x01, 0x06, 0x30, 0x0e, 0x04, 0x08, 0x41, 0x46, 0x22,
+    0xac, 0xe7, 0xd6, 0x7e, 0x61, 0x02, 0x02, 0x08, 0x00, 0x80, 0x82, 0x02,
+    0x30, 0x9a, 0x05, 0x55, 0x5a, 0xa0, 0xf6, 0xd4, 0x8c, 0x5e, 0x1c, 0x27,
+    0x91, 0x11, 0xfd, 0x1d, 0xe8, 0xfd, 0xae, 0xf2, 0xe6, 0x9f, 0x28, 0xb8,
+    0x1e, 0xfa, 0xce, 0x88, 0xb4, 0x23, 0xd6, 0xfa, 0x6e, 0x07, 0xe9, 0x33,
+    0x81, 0x70, 0x1d, 0xd0, 0x5e, 0x94, 0x04, 0xf1, 0x60, 0x8e, 0xbf, 0xe1,
+    0xef, 0xf4, 0xd7, 0xb2, 0x2f, 0x0d, 0xe9, 0x70, 0x2b, 0xe8, 0x62, 0xfc,
+    0xd3, 0x2a, 0x49, 0xf3, 0xf1, 0x06, 0x6f, 0x2a, 0x94, 0x8c, 0x42, 0xff,
+    0xc6, 0x80, 0xa8, 0x6a, 0xbf, 0xa3, 0x0a, 0xd3, 0x8e, 0x59, 0x52, 0xea,
+    0x60, 0xe8, 0x5a, 0x64, 0x23, 0xac, 0x8d, 0x40, 0x2d, 0xc9, 0xfe, 0x0b,
+    0xf3, 0x93, 0x52, 0xc3, 0x3e, 0xea, 0x34, 0x9a, 0xea, 0x42, 0x6a, 0xe4,
+    0x09, 0x25, 0x44, 0x5d, 0x5e, 0xb4, 0x3b, 0xfb, 0xe0, 0xc2, 0xdf, 0xd8,
+    0xaf, 0xae, 0x20, 0x59, 0xb0, 0x8c, 0xdd, 0xb3, 0x4a, 0x5f, 0xca, 0x6c,
+    0x2f, 0xe3, 0xb4, 0x99, 0xc6, 0x8f, 0x75, 0xc5, 0x72, 0x31, 0x0e, 0x4c,
+    0x46, 0xe6, 0xe1, 0xbf, 0x3f, 0xdf, 0x02, 0x7d, 0xde, 0x35, 0xad, 0xd9,
+    0x9d, 0xcb, 0x74, 0xa7, 0x5c, 0x52, 0x3b, 0xc2, 0x9c, 0x76, 0xbd, 0xf7,
+    0x96, 0xfc, 0xc5, 0x9d, 0xc7, 0xa7, 0x79, 0x30, 0xa0, 0x89, 0xd6, 0xd3,
+    0xa8, 0xe8, 0x63, 0xd2, 0x3a, 0x3f, 0x88, 0xc1, 0x22, 0x8c, 0x20, 0x9c,
+    0xa0, 0x23, 0x07, 0xc3, 0xe4, 0x0c, 0x36, 0x19, 0xa8, 0xa3, 0xc4, 0xbc,
+    0xbc, 0xd6, 0x3d, 0x80, 0xcb, 0x54, 0x91, 0xc4, 0xab, 0x02, 0xd2, 0x43,
+    0x30, 0xe5, 0x01, 0xbd, 0x25, 0xcd, 0xe4, 0x29, 0x55, 0x0f, 0x6e, 0x83,
+    0xb8, 0xfb, 0x70, 0xf2, 0x34, 0x9a, 0x15, 0xc6, 0x16, 0xdf, 0x89, 0xe4,
+    0xd4, 0x83, 0x26, 0x08, 0x62, 0x05, 0xa6, 0xea, 0xf3, 0x63, 0xc3, 0xb5,
+    0x69, 0x62, 0xf8, 0x60, 0x5c, 0x28, 0x21, 0x51, 0xa4, 0x43, 0x76, 0xdd,
+    0x41, 0x6d, 0xbd, 0x6d, 0x8e, 0x3c, 0x63, 0x44, 0xb6, 0xea, 0x3a, 0x2a,
+    0x1c, 0x9d, 0x4b, 0x84, 0xed, 0xbd, 0x2e, 0x3b, 0x97, 0x89, 0xc3, 0x88,
+    0xca, 0x5f, 0x84, 0x0f, 0xbd, 0x50, 0xeb, 0x94, 0x67, 0x83, 0xa7, 0x83,
+    0xdf, 0xd7, 0x9d, 0x81, 0x40, 0x3a, 0x7b, 0xcf, 0x8b, 0x1d, 0x19, 0x9b,
+    0xe1, 0x4e, 0xb4, 0x4b, 0x1d, 0x5b, 0x98, 0xa8, 0xe3, 0x89, 0xed, 0xf3,
+    0x48, 0xfc, 0x0d, 0x38, 0xd5, 0x42, 0x31, 0xe3, 0x79, 0x3a, 0xea, 0xa3,
+    0x4b, 0x58, 0xa3, 0x75, 0x7c, 0xd4, 0xc4, 0x38, 0x27, 0x9e, 0x97, 0x4e,
+    0xc1, 0x70, 0xa8, 0xee, 0x85, 0xe2, 0xb8, 0x53, 0x57, 0x15, 0x05, 0xbb,
+    0xf1, 0xb4, 0xfd, 0xe8, 0x24, 0x99, 0x64, 0xa7, 0xf3, 0x6a, 0xcc, 0x4b,
+    0xe9, 0x8d, 0x66, 0x38, 0x9a, 0x45, 0xe2, 0x73, 0x5e, 0x66, 0x18, 0xd9,
+    0x64, 0x46, 0xd7, 0xd1, 0x23, 0x30, 0xbe, 0xa2, 0x4b, 0x5c, 0x0e, 0x4c,
+    0x8a, 0x47, 0x88, 0xb4, 0x7a, 0x2e, 0x0f, 0xb6, 0xab, 0x2d, 0x56, 0x20,
+    0x76, 0xf4, 0xa1, 0x37, 0xb6, 0x6b, 0x98, 0x2a, 0xb4, 0xda, 0x67, 0xcb,
+    0x67, 0x5c, 0xc7, 0x2d, 0x41, 0xf6, 0x14, 0x0d, 0x6b, 0x16, 0x05, 0xe6,
+    0x0a, 0xa2, 0xf7, 0x03, 0x5e, 0xf8, 0x9c, 0x85, 0x58, 0xa5, 0x82, 0xa4,
+    0xaf, 0xd1, 0xf0, 0x3a, 0x48, 0xa1, 0x68, 0x10, 0xa4, 0xa5, 0xc5, 0x87,
+    0xf5, 0xc3, 0xf8, 0x94, 0x9d, 0x13, 0xcb, 0x08, 0x42, 0x14, 0xb3, 0x68,
+    0x68, 0x18, 0xec, 0xa9, 0x57, 0x9c, 0xeb, 0xc9, 0xe9, 0xaf, 0x7d, 0xcc,
+    0xb9, 0x4d, 0x58, 0x8d, 0xbf, 0x04, 0xb7, 0x1c, 0x3f, 0xfa, 0xd3, 0xb9,
+    0xb9, 0xad, 0x0e, 0xd2, 0x5f, 0x8b, 0x41, 0xfa, 0xdc, 0x85, 0x3e, 0x0a,
+    0xba, 0x49, 0x1b, 0xe2, 0x0c, 0xb6, 0x85, 0x9b, 0x24, 0x3c, 0xdf, 0x26,
+    0x9d, 0x05, 0x50, 0x64, 0x12, 0x96, 0x24, 0xdb, 0x4d, 0x79, 0x07, 0xa7,
+    0xb2, 0x3c, 0xf9, 0x42, 0xca, 0xda, 0x67, 0xc0, 0x6d, 0xf2, 0x7e, 0xbc,
+    0x1e, 0x5c, 0x2b, 0x4b, 0xf6, 0xf4, 0x35, 0x82, 0x70, 0x6b, 0x81, 0x16,
+    0xfc, 0xf1, 0xa9, 0x5f, 0x07, 0x2c, 0xe9, 0x1e, 0x3f, 0x30, 0x82, 0x01,
+    0x02, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x01,
+    0xa0, 0x81, 0xf4, 0x04, 0x81, 0xf1, 0x30, 0x81, 0xee, 0x30, 0x81, 0xeb,
+    0x06, 0x0b, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x0c, 0x0a, 0x01,
+    0x02, 0xa0, 0x81, 0xb4, 0x30, 0x81, 0xb1, 0x30, 0x1c, 0x06, 0x0a, 0x2a,
+    0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x0c, 0x01, 0x03, 0x30, 0x0e, 0x04,
+    0x08, 0x6f, 0xb9, 0x01, 0x93, 0x6c, 0x0d, 0x4d, 0xe1, 0x02, 0x02, 0x08,
+    0x00, 0x04, 0x81, 0x90, 0x07, 0x42, 0x6a, 0x5a, 0x4c, 0x41, 0x41, 0x38,
+    0xe4, 0x15, 0xc2, 0x85, 0x4e, 0x88, 0xc6, 0xd3, 0x6f, 0x9f, 0x25, 0xd8,
+    0x66, 0x86, 0xf3, 0x65, 0x5d, 0x51, 0x43, 0xd6, 0x03, 0x91, 0x4c, 0xeb,
+    0xbb, 0x75, 0xce, 0x8b, 0xf4, 0x47, 0x43, 0x4c, 0x1a, 0x4b, 0x48, 0x92,
+    0xf4, 0xaf, 0x0a, 0x5f, 0x49, 0x96, 0xea, 0xaf, 0x31, 0x29, 0x7b, 0xa3,
+    0xb5, 0xd3, 0xe4, 0x67, 0x0c, 0x20, 0x0e, 0x52, 0x9e, 0xcf, 0xcf, 0x6a,
+    0x2d, 0x45, 0x38, 0x52, 0x61, 0xbf, 0x10, 0x2b, 0xc1, 0xc5, 0xde, 0x04,
+    0x1d, 0x0a, 0x52, 0x88, 0x07, 0x39, 0xc2, 0xc1, 0xd0, 0x44, 0x39, 0x9f,
+    0x46, 0xf2, 0x69, 0xa4, 0x30, 0x5b, 0xe4, 0x60, 0x68, 0x69, 0xb0, 0x95,
+    0x78, 0x05, 0xef, 0xe1, 0x81, 0xc2, 0xd2, 0x4e, 0x29, 0x52, 0x39, 0x51,
+    0xfc, 0x3d, 0x28, 0xe1, 0x7b, 0x58, 0x76, 0xcf, 0x35, 0x33, 0x2f, 0xef,
+    0x95, 0x76, 0x0c, 0x52, 0x11, 0x69, 0x17, 0x3c, 0x56, 0x36, 0xc6, 0xe1,
+    0x9c, 0x1c, 0xd4, 0x23, 0x31, 0x25, 0x30, 0x23, 0x06, 0x09, 0x2a, 0x86,
+    0x48, 0x86, 0xf7, 0x0d, 0x01, 0x09, 0x15, 0x31, 0x16, 0x04, 0x14, 0x3f,
+    0x31, 0x38, 0xec, 0xb9, 0xf1, 0x45, 0xe1, 0x3e, 0x90, 0x71, 0x0d, 0xc1,
+    0x28, 0xba, 0x4e, 0x6f, 0xa0, 0x9c, 0xed, 0x30, 0x31, 0x30, 0x21, 0x30,
+    0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14,
+    0x52, 0x8c, 0x3f, 0x72, 0x8c, 0xcf, 0x3a, 0xeb, 0xc8, 0xff, 0xc2, 0x8c,
+    0x48, 0x42, 0xa6, 0x1c, 0x42, 0x6e, 0x18, 0x43, 0x04, 0x08, 0xea, 0xec,
+    0xdc, 0xf6, 0xc4, 0xdf, 0xda, 0xd6, 0x02, 0x02, 0x08, 0x00};
+
+static const char kUnicodePassword[] = u8"Hello, 世界";
+
+static void TestImpl(const char *name, bssl::Span<const uint8_t> der,
+                     const char *password) {
   bssl::UniquePtr<STACK_OF(X509)> certs(sk_X509_new_null());
   ASSERT_TRUE(certs);
 
-  CBS pkcs12;
   EVP_PKEY *key = nullptr;
-  CBS_init(&pkcs12, der, der_len);
-  ASSERT_TRUE(PKCS12_get_key_and_certs(&key, certs.get(), &pkcs12, kPassword));
+  CBS pkcs12 = der;
+  ASSERT_TRUE(PKCS12_get_key_and_certs(&key, certs.get(), &pkcs12, password));
   bssl::UniquePtr<EVP_PKEY> delete_key(key);
 
   ASSERT_EQ(1u, sk_X509_num(certs.get()));
   ASSERT_TRUE(key);
 }
 
-static void TestCompat(const uint8_t *der, size_t der_len) {
-  bssl::UniquePtr<BIO> bio(BIO_new_mem_buf(der, der_len));
+static void TestCompat(bssl::Span<const uint8_t> der) {
+  bssl::UniquePtr<BIO> bio(BIO_new_mem_buf(der.data(), der.size()));
   ASSERT_TRUE(bio);
 
   bssl::UniquePtr<PKCS12> p12(d2i_PKCS12_bio(bio.get(), nullptr));
@@ -938,21 +1027,25 @@
 }
 
 TEST(PKCS12Test, TestOpenSSL) {
-  TestImpl("OpenSSL", kOpenSSL, sizeof(kOpenSSL));
+  TestImpl("OpenSSL", kOpenSSL, kPassword);
 }
 
 TEST(PKCS12Test, TestNSS) {
-  TestImpl("NSS", kNSS, sizeof(kNSS));
+  TestImpl("NSS", kNSS, kPassword);
 }
 
 TEST(PKCS12Test, TestWindows) {
-  TestImpl("Windows", kWindows, sizeof(kWindows));
+  TestImpl("Windows", kWindows, kPassword);
 }
 
 TEST(PKCS12Test, TestPBES2) {
-  TestImpl("PBES2", kPBES2, sizeof(kPBES2));
+  TestImpl("PBES2", kPBES2, kPassword);
+}
+
+TEST(PKCS12Test, TestUnicode) {
+  TestImpl("Unicode", kUnicode, kUnicodePassword);
 }
 
 TEST(PKCS12Test, TestWindowsCompat) {
-  TestCompat(kWindows, sizeof(kWindows));
+  TestCompat(kWindows);
 }
diff --git a/crypto/pkcs8/pkcs8.c b/crypto/pkcs8/pkcs8.c
index 94205e6..086e9a8 100644
--- a/crypto/pkcs8/pkcs8.c
+++ b/crypto/pkcs8/pkcs8.c
@@ -68,32 +68,42 @@
 #include <openssl/rand.h>
 
 #include "internal.h"
+#include "../bytestring/internal.h"
 #include "../internal.h"
 
 
-static int ascii_to_ucs2(const char *ascii, size_t ascii_len,
-                         uint8_t **out, size_t *out_len) {
-  size_t ulen = ascii_len * 2 + 2;
-  if (ascii_len * 2 < ascii_len || ulen < ascii_len * 2) {
-    return 0;
-  }
-
-  uint8_t *unitmp = OPENSSL_malloc(ulen);
-  if (unitmp == NULL) {
+static int pkcs12_encode_password(const char *in, size_t in_len, uint8_t **out,
+                                  size_t *out_len) {
+  CBB cbb;
+  if (!CBB_init(&cbb, in_len * 2)) {
     OPENSSL_PUT_ERROR(PKCS8, ERR_R_MALLOC_FAILURE);
     return 0;
   }
-  for (size_t i = 0; i < ulen - 2; i += 2) {
-    unitmp[i] = 0;
-    unitmp[i + 1] = ascii[i >> 1];
+
+  // Convert the password to BMPString, or UCS-2. See
+  // https://tools.ietf.org/html/rfc7292#appendix-B.1.
+  CBS cbs;
+  CBS_init(&cbs, (const uint8_t *)in, in_len);
+  while (CBS_len(&cbs) != 0) {
+    uint32_t c;
+    if (!cbs_get_utf8(&cbs, &c) ||
+        !cbb_add_ucs2_be(&cbb, c)) {
+      OPENSSL_PUT_ERROR(PKCS8, PKCS8_R_INVALID_CHARACTERS);
+      goto err;
+    }
   }
 
   // Terminate the result with a UCS-2 NUL.
-  unitmp[ulen - 2] = 0;
-  unitmp[ulen - 1] = 0;
-  *out_len = ulen;
-  *out = unitmp;
+  if (!cbb_add_ucs2_be(&cbb, 0) ||
+      !CBB_finish(&cbb, out, out_len)) {
+    goto err;
+  }
+
   return 1;
+
+err:
+  CBB_cleanup(&cbb);
+  return 0;
 }
 
 int pkcs12_key_gen(const char *pass, size_t pass_len, const uint8_t *salt,
@@ -115,7 +125,7 @@
   // If |pass| is NULL, we use the empty string rather than {0, 0} as the raw
   // password.
   if (pass != NULL &&
-      !ascii_to_ucs2(pass, pass_len, &pass_raw, &pass_raw_len)) {
+      !pkcs12_encode_password(pass, pass_len, &pass_raw, &pass_raw_len)) {
     goto err;
   }
 
diff --git a/include/openssl/pkcs8.h b/include/openssl/pkcs8.h
index f865c76..f84906f 100644
--- a/include/openssl/pkcs8.h
+++ b/include/openssl/pkcs8.h
@@ -226,5 +226,6 @@
 #define PKCS8_R_UNSUPPORTED_KEY_DERIVATION_FUNCTION 128
 #define PKCS8_R_BAD_ITERATION_COUNT 129
 #define PKCS8_R_UNSUPPORTED_PRF 130
+#define PKCS8_R_INVALID_CHARACTERS 131
 
 #endif  // OPENSSL_HEADER_PKCS8_H