diff --git a/src/tvheadend.h b/src/tvheadend.h
index 23018afe..a601f80e 100644
--- a/src/tvheadend.h
+++ b/src/tvheadend.h
@@ -454,7 +454,7 @@ int tvh_socket(int domain, int type, int protocol);
 
 int tvh_pipe(int flags, th_pipe_t *pipe);
 
-int tvh_write(int fd, void *buf, size_t len);
+int tvh_write(int fd, const void *buf, size_t len);
 
 void hexdump(const char *pfx, const uint8_t *data, int len);
 
diff --git a/src/wrappers.c b/src/wrappers.c
index febe6a8c..5b08d3ce 100644
--- a/src/wrappers.c
+++ b/src/wrappers.c
@@ -50,7 +50,7 @@ tvh_pipe(int flags, th_pipe_t *p)
 }
 
 int
-tvh_write(int fd, void *buf, size_t len)
+tvh_write(int fd, const void *buf, size_t len)
 {
   ssize_t c;