1 files changed, 3 insertions, 3 deletions
diff --git a/gr-blocks/lib/ctrlport_probe2_c_impl.h b/gr-blocks/lib/ctrlport_probe2_c_impl.h
index a0d3262755..b6d94f91ef 100644
--- a/gr-blocks/lib/ctrlport_probe2_c_impl.h
+++ b/gr-blocks/lib/ctrlport_probe2_c_impl.h
@@ -21,10 +21,10 @@ namespace blocks {
 class ctrlport_probe2_c_impl : public ctrlport_probe2_c
 {
 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<gr_complex> d_buffer;