diff --git a/lib/includes/spdylay/spdylay.h b/lib/includes/spdylay/spdylay.h
index 82df6a8d..a23478c7 100644
--- a/lib/includes/spdylay/spdylay.h
+++ b/lib/includes/spdylay/spdylay.h
@@ -401,9 +401,10 @@ void* spdylay_session_get_stream_user_data(spdylay_session *session,
  * range of [0, 3]. 0 means the higest priority. |nv| must include
  * following name/value pairs:
  *
- * "method": HTTP method (e.g., "GET" or "POST")
+ * "method": HTTP method (e.g., "GET", "POST", "HEAD", etc)
  * "scheme": URI scheme (e.g., "https")
- * "url": Absolute path of this request (e.g., "/foo")
+ * "url": Absolute path and parameters of this request (e.g., "/foo",
+ * "/foo;bar;haz?h=j&y=123")
  * "version": HTTP version (e.g., "HTTP/1.1")
  *
  * "host" name/value pair is also required by some hosts.
@@ -412,11 +413,12 @@ void* spdylay_session_get_stream_user_data(spdylay_session *session,
  * also lower-cases all names in |nv|.
  *
  * If |data_prd| is not NULL, it provides data which will be sent in
- * subsequent DATA frames. In this case, "POST" must be specified with
- * "method" key in |nv|. If |data_prd| is NULL, SYN_STREAM have
- * FLAG_FIN.  |stream_user_data| can be an arbitrary pointer, which
- * can be retrieved by spdylay_session_get_stream_user_data(). Since
- * stream ID is not known before sending SYN_STREAM frame and the
+ * subsequent DATA frames. In this case, a method that allows request
+ * message bodies (http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9)
+ * must be specified with "method" key in |nv| (e.g. POST). If |data_prd| is
+ * NULL, SYN_STREAM have * FLAG_FIN.  |stream_user_data| can be an arbitrary
+ * pointer, which can be retrieved by spdylay_session_get_stream_user_data().
+ * Since stream ID is not known before sending SYN_STREAM frame and the
  * application code has to compare url, and possibly other header
  * field values, to identify stream ID for the request in
  * spdylay_on_ctrl_send_callback(). With |stream_user_data|, the
diff --git a/lib/spdylay_submit.c b/lib/spdylay_submit.c
index 86245a09..2b156810 100644
--- a/lib/spdylay_submit.c
+++ b/lib/spdylay_submit.c
@@ -124,7 +124,7 @@ int spdylay_submit_request(spdylay_session *session, uint8_t pri,
   if(pri > 3) {
     return SPDYLAY_ERR_INVALID_ARGUMENT;
   }
-  if(data_prd) {
+  if(data_prd != NULL && data_prd->read_callback != NULL) {
     data_prd_copy = malloc(sizeof(spdylay_data_provider));
     if(data_prd_copy == NULL) {
       return SPDYLAY_ERR_NOMEM;
diff --git a/tests/main.c b/tests/main.c
index f144a84f..f670504b 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -134,6 +134,8 @@ int main(int argc, char* argv[])
       !CU_add_test(pSuite, "frame_nv_sort", test_spdylay_frame_nv_sort) ||
       !CU_add_test(pSuite, "frame_nv_downcase",
                    test_spdylay_frame_nv_downcase) ||
+      !CU_add_test(pSuite, "frame_nv_downcase",
+                   test_spdylay_frame_pack_nv_duplicate_keys) ||
       !CU_add_test(pSuite, "stream_add_pushed_stream",
                    test_spdylay_stream_add_pushed_stream)) {
      CU_cleanup_registry();
diff --git a/tests/spdylay_frame_test.c b/tests/spdylay_frame_test.c
index c57f66d5..f73199c2 100644
--- a/tests/spdylay_frame_test.c
+++ b/tests/spdylay_frame_test.c
@@ -60,6 +60,92 @@ void test_spdylay_frame_unpack_nv()
   spdylay_frame_nv_del(nv);
 }
 
+void test_spdylay_frame_pack_nv_duplicate_keys()
+{
+  int i;
+  uint8_t out[1024];
+  const char *nv_src[] = {
+    "method", "GET",
+    "scheme", "https",
+    "url", "/",
+    "X-hEad", "foo",
+    "x-heaD", "bar",
+    "version", "HTTP/1.1",
+    NULL
+  };
+  char **nv = spdylay_frame_nv_copy(nv_src);
+  spdylay_frame_nv_downcase(nv);
+  spdylay_frame_nv_sort(nv);
+  size_t inlen = spdylay_frame_pack_nv(out, nv);
+  const uint8_t *outptr = out;
+  int pairs = spdylay_get_uint16(outptr);
+  CU_ASSERT(pairs == 5);
+  outptr += 2;
+
+  int len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 6);
+  CU_ASSERT(memcmp(outptr, "method", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 3);
+  CU_ASSERT(memcmp(outptr, "GET", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 6);
+  CU_ASSERT(memcmp(outptr, "scheme", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 5);
+  CU_ASSERT(memcmp(outptr, "https", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 3);
+  CU_ASSERT(memcmp(outptr, "url", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 1);
+  CU_ASSERT(memcmp(outptr, "/", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 7);
+  CU_ASSERT(memcmp(outptr, "version", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 8);
+  CU_ASSERT(memcmp(outptr, "HTTP/1.1", len) == 0);
+  outptr += len;
+
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 6);
+  CU_ASSERT(memcmp(outptr, "x-head", len) == 0);
+  outptr += len;
+
+  len = spdylay_get_uint16(outptr);
+  outptr += 2;
+  CU_ASSERT(len == 7);
+  CU_ASSERT(memcmp(outptr, "foo\0bar", len) == 0);
+  outptr += len;
+
+  spdylay_frame_nv_del(nv);
+}
+
 void test_spdylay_frame_count_nv_space()
 {
   CU_ASSERT(83 == spdylay_frame_count_nv_space((char**)headers));
diff --git a/tests/spdylay_frame_test.h b/tests/spdylay_frame_test.h
index 6484e565..7c62e836 100644
--- a/tests/spdylay_frame_test.h
+++ b/tests/spdylay_frame_test.h
@@ -26,6 +26,7 @@
 #define SPDYLAY_FRAME_TEST_H
 
 void test_spdylay_frame_unpack_nv();
+void test_spdylay_frame_pack_nv_duplicate_keys();
 void test_spdylay_frame_count_nv_space();
 void test_spdylay_frame_count_unpack_nv_space();
 void test_spdylay_frame_pack_ping();