diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index 2f13a797..940980eb 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -2540,7 +2540,7 @@ int32_t nghttp2_submit_push_promise(nghttp2_session *session, uint8_t flags,
  *     Out of memory.
  */
 int nghttp2_submit_ping(nghttp2_session *session, uint8_t flags,
-                        uint8_t *opaque_data);
+                        const uint8_t *opaque_data);
 
 /**
  * @function
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index c1a48752..014fcd6b 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -5133,7 +5133,7 @@ int nghttp2_session_want_write(nghttp2_session *session)
 }
 
 int nghttp2_session_add_ping(nghttp2_session *session, uint8_t flags,
-                             uint8_t *opaque_data)
+                             const uint8_t *opaque_data)
 {
   int rv;
   nghttp2_frame *frame;
diff --git a/lib/nghttp2_session.h b/lib/nghttp2_session.h
index 5ba7af5a..871fca6f 100644
--- a/lib/nghttp2_session.h
+++ b/lib/nghttp2_session.h
@@ -295,7 +295,7 @@ int nghttp2_session_add_rst_stream(nghttp2_session *session,
  *     Out of memory.
  */
 int nghttp2_session_add_ping(nghttp2_session *session, uint8_t flags,
-                             uint8_t *opaque_data);
+                             const uint8_t *opaque_data);
 
 /*
  * Adds GOAWAY frame with the last-stream-ID |last_stream_id| and the
diff --git a/lib/nghttp2_submit.c b/lib/nghttp2_submit.c
index 1a7a3b56..748d47d6 100644
--- a/lib/nghttp2_submit.c
+++ b/lib/nghttp2_submit.c
@@ -189,7 +189,7 @@ int32_t nghttp2_submit_headers(nghttp2_session *session, uint8_t flags,
 
 
 int nghttp2_submit_ping(nghttp2_session *session, uint8_t flags,
-                        uint8_t *opaque_data)
+                        const uint8_t *opaque_data)
 {
   return nghttp2_session_add_ping(session, NGHTTP2_FLAG_NONE, opaque_data);
 }