diff --git a/core/equipment.c b/core/equipment.c
index 81033ace6..09778dfa1 100644
--- a/core/equipment.c
+++ b/core/equipment.c
@@ -18,7 +18,7 @@
 #include "divelist.h"
 
 /* placeholders for a few functions that we need to redesign for the Qt UI */
-void add_cylinder_description(cylinder_type_t *type)
+void add_cylinder_description(const cylinder_type_t *type)
 {
 	const char *desc;
 	int i;
@@ -37,7 +37,7 @@ void add_cylinder_description(cylinder_type_t *type)
 		tank_info[i].bar = type->workingpressure.mbar / 1000;
 	}
 }
-void add_weightsystem_description(weightsystem_t *weightsystem)
+void add_weightsystem_description(const weightsystem_t *weightsystem)
 {
 	const char *desc;
 	int i;
diff --git a/core/equipment.h b/core/equipment.h
index eb789ede8..e4c654689 100644
--- a/core/equipment.h
+++ b/core/equipment.h
@@ -46,8 +46,8 @@ typedef struct
 #define W_IDX_PRIMARY 0
 #define W_IDX_SECONDARY 1
 
-extern void add_cylinder_description(cylinder_type_t *);
-extern void add_weightsystem_description(weightsystem_t *);
+extern void add_cylinder_description(const cylinder_type_t *);
+extern void add_weightsystem_description(const weightsystem_t *);
 extern bool cylinder_nodata(const cylinder_t *cyl);
 extern bool cylinder_none(const cylinder_t *cyl);
 extern bool weightsystem_none(const weightsystem_t *ws);