1 files changed, 3 insertions, 3 deletions
diff --git a/gr-blocks/lib/ctrlport_probe2_f_impl.h b/gr-blocks/lib/ctrlport_probe2_f_impl.h
index 08a3b011af..75ed009098 100644
--- a/gr-blocks/lib/ctrlport_probe2_f_impl.h
+++ b/gr-blocks/lib/ctrlport_probe2_f_impl.h
@@ -21,10 +21,10 @@ namespace blocks {
 class ctrlport_probe2_f_impl : public ctrlport_probe2_f
 {
 private:
-    std::string d_id;
-    std::string d_desc;
+    const std::string d_id;
+    const std::string d_desc;
     size_t d_len;
-    unsigned int d_disp_mask;
+    const unsigned int d_disp_mask;
 
     size_t d_index;
     std::vector<float> d_buffer;