diff --git a/crypto/asn1/asn1_test.cc b/crypto/asn1/asn1_test.cc
index 6fa3f95..e6847c8 100644
--- a/crypto/asn1/asn1_test.cc
+++ b/crypto/asn1/asn1_test.cc
@@ -1023,6 +1023,18 @@
   }
 }
 
+// Test that multi-string types correctly encode negative ENUMERATED.
+// Multi-string types cannot contain INTEGER, so we only test ENUMERATED.
+TEST(ASN1Test, NegativeEnumeratedMultistring) {
+  static const uint8_t kMinusOne[] = {0x0a, 0x01, 0xff};  // ENUMERATED { -1 }
+  // |ASN1_PRINTABLE| is a multi-string type that allows ENUMERATED.
+  const uint8_t *p = kMinusOne;
+  bssl::UniquePtr<ASN1_STRING> str(
+      d2i_ASN1_PRINTABLE(nullptr, &p, sizeof(kMinusOne)));
+  ASSERT_TRUE(str);
+  TestSerialize(str.get(), i2d_ASN1_PRINTABLE, kMinusOne);
+}
+
 // The ASN.1 macros do not work on Windows shared library builds, where usage of
 // |OPENSSL_EXPORT| is a bit stricter.
 #if !defined(OPENSSL_WINDOWS) || !defined(BORINGSSL_SHARED_LIBRARY)
diff --git a/crypto/asn1/tasn_enc.c b/crypto/asn1/tasn_enc.c
index 95d8611..142de6d 100644
--- a/crypto/asn1/tasn_enc.c
+++ b/crypto/asn1/tasn_enc.c
@@ -525,6 +525,20 @@
         /* If MSTRING type set the underlying type */
         strtmp = (ASN1_STRING *)*pval;
         utype = strtmp->type;
+        /* Negative INTEGER and ENUMERATED values use |ASN1_STRING| type values
+         * that do not match their corresponding utype values. INTEGERs cannot
+         * participate in MSTRING types, but ENUMERATEDs can.
+         *
+         * TODO(davidben): Is this a bug? Although arguably one of the MSTRING
+         * types should contain more values, rather than less. See
+         * https://crbug.com/boringssl/412. But it is not possible to fit all
+         * possible ANY values into an |ASN1_STRING|, so matching the spec here
+         * is somewhat hopeless. */
+        if (utype == V_ASN1_NEG_INTEGER) {
+            utype = V_ASN1_INTEGER;
+        } else if (utype == V_ASN1_NEG_ENUMERATED) {
+            utype = V_ASN1_ENUMERATED;
+        }
         *putype = utype;
     } else if (it->utype == V_ASN1_ANY) {
         /* If ANY set type and pointer to value */