diff --git a/crypto/asn1/a_strex.c b/crypto/asn1/a_strex.c
index b9b6f1c871..b31761aae6 100644
--- a/crypto/asn1/a_strex.c
+++ b/crypto/asn1/a_strex.c
@@ -280,6 +280,8 @@ static int do_dump(unsigned long lflags, char_io *io_ch, void *arg,
     t.type = str->type;
     t.value.ptr = (char *)str;
     der_len = i2d_ASN1_TYPE(&t, NULL);
+    if (der_len <= 0)
+        return -1;
     if ((der_buf = OPENSSL_malloc(der_len)) == NULL) {
         ERR_raise(ERR_LIB_ASN1, ERR_R_MALLOC_FAILURE);
         return -1;