diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index bf6b55ee830..ae94cc99d31 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -227,7 +227,7 @@ PostmasterChildName(BackendType child_type)
  */
 pid_t
 postmaster_child_launch(BackendType child_type, int child_slot,
-						const void *startup_data, size_t startup_data_len,
+						void *startup_data, size_t startup_data_len,
 						ClientSocket *client_sock)
 {
 	pid_t		pid;
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index 92497cd6a0f..753871071ac 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -108,7 +108,7 @@ extern PGDLLIMPORT struct ClientSocket *MyClientSocket;
 /* prototypes for functions in launch_backend.c */
 extern pid_t postmaster_child_launch(BackendType child_type,
 									 int child_slot,
-									 const void *startup_data,
+									 void *startup_data,
 									 size_t startup_data_len,
 									 struct ClientSocket *client_sock);
 const char *PostmasterChildName(BackendType child_type);