diff --git a/crypto/asn1/a_strex.c b/crypto/asn1/a_strex.c
index b8f6626..4329493 100644
--- a/crypto/asn1/a_strex.c
+++ b/crypto/asn1/a_strex.c
@@ -303,6 +303,20 @@
      */
     ASN1_TYPE t;
     t.type = str->type;
+    /* Negative INTEGER and ENUMERATED values are the only case where
+     * |ASN1_STRING| and |ASN1_TYPE| types do not match.
+     *
+     * TODO(davidben): There are also some type fields which, in |ASN1_TYPE|, do
+     * not correspond to |ASN1_STRING|. It is unclear whether those are allowed
+     * in |ASN1_STRING| at all, or what the space of allowed types is.
+     * |ASN1_item_ex_d2i| will never produce such a value so, for now, we say
+     * this is an invalid input. But this corner of the library in general
+     * should be more robust. */
+    if (t.type == V_ASN1_NEG_INTEGER) {
+      t.type = V_ASN1_INTEGER;
+    } else if (t.type == V_ASN1_NEG_ENUMERATED) {
+      t.type = V_ASN1_ENUMERATED;
+    }
     t.value.asn1_string = (ASN1_STRING *)str;
     unsigned char *der_buf = NULL;
     int der_len = i2d_ASN1_TYPE(&t, &der_buf);
diff --git a/crypto/asn1/asn1_test.cc b/crypto/asn1/asn1_test.cc
index 0d9c43c..76f87bf 100644
--- a/crypto/asn1/asn1_test.cc
+++ b/crypto/asn1/asn1_test.cc
@@ -721,6 +721,30 @@
        ASN1_STRING_FLAG_BITS_LEFT | 4,
        ASN1_STRFLGS_DUMP_ALL | ASN1_STRFLGS_DUMP_DER,
        "#03020480"},
+      // INTEGER { 1 }
+      {V_ASN1_INTEGER,
+       {0x01},
+       0,
+       ASN1_STRFLGS_DUMP_ALL | ASN1_STRFLGS_DUMP_DER,
+       "#020101"},
+      // INTEGER { -1 }
+      {V_ASN1_NEG_INTEGER,
+       {0x01},
+       0,
+       ASN1_STRFLGS_DUMP_ALL | ASN1_STRFLGS_DUMP_DER,
+       "#0201FF"},
+      // ENUMERATED { 1 }
+      {V_ASN1_ENUMERATED,
+       {0x01},
+       0,
+       ASN1_STRFLGS_DUMP_ALL | ASN1_STRFLGS_DUMP_DER,
+       "#0A0101"},
+      // ENUMERATED { -1 }
+      {V_ASN1_NEG_ENUMERATED,
+       {0x01},
+       0,
+       ASN1_STRFLGS_DUMP_ALL | ASN1_STRFLGS_DUMP_DER,
+       "#0A01FF"},
   };
   for (const auto &t : kTests) {
     SCOPED_TRACE(t.type);