diff --git a/src/mesa/state_tracker/st_format.c b/src/mesa/state_tracker/st_format.c
index 99527b74bab..7901d50b713 100644
--- a/src/mesa/state_tracker/st_format.c
+++ b/src/mesa/state_tracker/st_format.c
@@ -58,7 +58,7 @@
  * Translate Mesa format to Gallium format.
  */
 enum pipe_format
-st_mesa_format_to_pipe_format(struct st_context *st, mesa_format mesaFormat)
+st_mesa_format_to_pipe_format(const struct st_context *st, mesa_format mesaFormat)
 {
    switch (mesaFormat) {
    case MESA_FORMAT_A8B8G8R8_UNORM:
diff --git a/src/mesa/state_tracker/st_format.h b/src/mesa/state_tracker/st_format.h
index 6ba61df7e4e..3dd9c10341a 100644
--- a/src/mesa/state_tracker/st_format.h
+++ b/src/mesa/state_tracker/st_format.h
@@ -45,7 +45,7 @@ struct pipe_screen;
 
 
 extern enum pipe_format
-st_mesa_format_to_pipe_format(struct st_context *st, mesa_format mesaFormat);
+st_mesa_format_to_pipe_format(const struct st_context *st, mesa_format mesaFormat);
 
 extern mesa_format
 st_pipe_format_to_mesa_format(enum pipe_format pipeFormat);