diff --git a/fs_edit_general.lua b/fs_edit_general.lua
index dd41af7..9c70656 100644
--- a/fs_edit_general.lua
+++ b/fs_edit_general.lua
@@ -1011,6 +1011,22 @@ yl_speak_up.input_fs_edit_option_related = function(player, formname, fields,
 				})
 			return
 		end
+	-- allow to delete unused variables
+	elseif(fields.delete_unused_variable) then
+		-- try to delete the variable
+		local res = yl_speak_up.del_quest_variable(pname, data.variable_name)
+		local text = "Deleted successfully."
+		if(not(res)) then
+			text = "Error: Variable could not be deleted."
+		end
+		yl_speak_up.show_fs(player, "msg", {
+			input_to = "yl_speak_up:"..formspec_input_to,
+			formspec = "size[8,2]"..
+				"label[0.2,0.5;Trying to delete variable \""..
+					minetest.formspec_escape(tostring(data.variable_name))..
+					"\":\n"..text.."]"..
+				"button[1.5,1.5;2,0.9;back_from_error_msg;Back]"})
+		return
 	end
 
 	-- the player wants to change/edit a precondition or effect
diff --git a/quest_api.lua b/quest_api.lua
index 4f49293..092bc47 100644
--- a/quest_api.lua
+++ b/quest_api.lua
@@ -74,13 +74,15 @@ end
 
 -- accidentally created or no longer needed variables need to be deleted somehow
 yl_speak_up.del_quest_variable = function(owner_name, variable_name)
-	local k = "$ "..tostring(owner_name).." "..tostring(variable_name)
+	local k = yl_speak_up.restore_complete_var_name(variable_name, owner_name)
 	if(not(owner_name) or not(variable_name)) then
 		return false
 	end
+	-- actually delete the variable
+	yl_speak_up.player_vars[ k ] = nil
 	-- a variable was deleted - that deserves a forced save
 	yl_speak_up.save_quest_variables(true)
-	yl_speak_up.player_vars[ k ] = nil
+	return true
 end
 
 
@@ -250,6 +252,18 @@ yl_speak_up.strip_pname_from_varlist = function(var_list, pname)
 end
 
 
+-- (partly) the opposite of the function above - add the name of the player to a variable
+-- name again if needed
+yl_speak_up.restore_complete_var_name = function(var_name, pname)
+	local vparts = string.split(var_name or "", " ")
+	-- has the player name been stripped from the variable name for better readability?
+	if(vparts and #vparts > 0 and vparts[1] ~= "$") then
+		return "$ "..tostring(pname).." "..table.concat(vparts, " ")
+	end
+	return var_name
+end
+
+
 -- helper function for saving NPC data;
 -- this only works if *someone* is currently talking to that NPC
 yl_speak_up.get_pname_for_n_id = function(n_id)
@@ -370,6 +384,7 @@ end
 
 -- which NPC do use this variable?
 yl_speak_up.get_npc_users_of_variable = function(var_name)
+	var_name = yl_speak_up.restore_complete_var_name(var_name, pname)
 	-- no variable, or nothing stored? then it's not used by any NPC either
 	if(not(var_name)
 	  or not(yl_speak_up.player_vars[ var_name ])
@@ -413,6 +428,7 @@ end
 -- find out where this variable is used in NPCs
 yl_speak_up.get_list_of_usage_of_variable = function(var_name, pname, check_preconditions,
 						back_button_name, back_button_text)
+	var_name = yl_speak_up.restore_complete_var_name(var_name, pname)
 	-- which NPC (might be several) is using this variable?
 	local npc_list = yl_speak_up.get_npc_users_of_variable(var_name)
 	-- list of all relevant preconditions, actions and effects