diff --git a/lib/includes/spdylay/spdylay.h b/lib/includes/spdylay/spdylay.h
index 078f7b15..7ddc8aee 100644
--- a/lib/includes/spdylay/spdylay.h
+++ b/lib/includes/spdylay/spdylay.h
@@ -483,7 +483,7 @@ void* spdylay_session_get_stream_user_data(spdylay_session *session,
  */
 int spdylay_submit_request(spdylay_session *session, uint8_t pri,
                            const char **nv,
-                           spdylay_data_provider *data_prd,
+                           const spdylay_data_provider *data_prd,
                            void *stream_user_data);
 
 /*
@@ -509,7 +509,7 @@ int spdylay_submit_request(spdylay_session *session, uint8_t pri,
  */
 int spdylay_submit_response(spdylay_session *session,
                             int32_t stream_id, const char **nv,
-                            spdylay_data_provider *data_prd);
+                            const spdylay_data_provider *data_prd);
 
 /*
  * Submits SYN_STREAM frame. The |flags| is bitwise OR of the
@@ -554,7 +554,7 @@ int spdylay_submit_syn_stream(spdylay_session *session, uint8_t flags,
  *     Out of memory.
  */
 int spdylay_submit_data(spdylay_session *session, int32_t stream_id,
-                        uint8_t flags, spdylay_data_provider *data_prd);
+                        uint8_t flags, const spdylay_data_provider *data_prd);
 
 /*
  * Submits RST_STREAM frame to cancel/reject stream |stream_id| with
diff --git a/lib/spdylay_frame.c b/lib/spdylay_frame.c
index 2f78715a..23d7d2a1 100644
--- a/lib/spdylay_frame.c
+++ b/lib/spdylay_frame.c
@@ -478,7 +478,8 @@ void spdylay_frame_settings_free(spdylay_settings *frame)
 }
 
 void spdylay_frame_data_init(spdylay_data *frame, int32_t stream_id,
-                             uint8_t flags, spdylay_data_provider *data_prd)
+                             uint8_t flags,
+                             const spdylay_data_provider *data_prd)
 {
   memset(frame, 0, sizeof(spdylay_data));
   frame->stream_id = stream_id;
diff --git a/lib/spdylay_frame.h b/lib/spdylay_frame.h
index 261455be..7acb312f 100644
--- a/lib/spdylay_frame.h
+++ b/lib/spdylay_frame.h
@@ -429,7 +429,8 @@ void spdylay_frame_settings_init(spdylay_settings *frame, uint8_t flags,
 void spdylay_frame_settings_free(spdylay_settings *frame);
 
 void spdylay_frame_data_init(spdylay_data *frame, int32_t stream_id,
-                             uint8_t flags, spdylay_data_provider *data_prd);
+                             uint8_t flags,
+                             const spdylay_data_provider *data_prd);
 
 void spdylay_frame_data_free(spdylay_data *frame);
 
diff --git a/lib/spdylay_submit.c b/lib/spdylay_submit.c
index 91fa3864..920bf3fc 100644
--- a/lib/spdylay_submit.c
+++ b/lib/spdylay_submit.c
@@ -124,7 +124,8 @@ int spdylay_submit_goaway(spdylay_session *session)
 }
 
 int spdylay_submit_request(spdylay_session *session, uint8_t pri,
-                           const char **nv, spdylay_data_provider *data_prd,
+                           const char **nv,
+                           const spdylay_data_provider *data_prd,
                            void *stream_user_data)
 {
   int flags;
@@ -138,7 +139,7 @@ int spdylay_submit_request(spdylay_session *session, uint8_t pri,
 
 int spdylay_submit_response(spdylay_session *session,
                             int32_t stream_id, const char **nv,
-                            spdylay_data_provider *data_prd)
+                            const spdylay_data_provider *data_prd)
 {
   int r;
   spdylay_frame *frame;
@@ -182,7 +183,7 @@ int spdylay_submit_response(spdylay_session *session,
 
 int spdylay_submit_data(spdylay_session *session, int32_t stream_id,
                         uint8_t flags,
-                        spdylay_data_provider *data_prd)
+                        const spdylay_data_provider *data_prd)
 {
   int r;
   spdylay_frame *frame;