diff --git a/bacnet-stack/include/indtext.h b/bacnet-stack/include/indtext.h
index 80febaa7..4c53b0e0 100644
--- a/bacnet-stack/include/indtext.h
+++ b/bacnet-stack/include/indtext.h
@@ -29,8 +29,8 @@
 #include <string.h>
 
 /* index and text pairs */
-typedef struct {
-    unsigned index;     /* index number that matches the text */
+const typedef struct {
+    const unsigned index;     /* index number that matches the text */
     const char *pString;        /* text pair - use NULL to end the list */
 } INDTEXT_DATA;