diff --git a/include/m908/getters.cpp b/include/m908/getters.cpp
index 7da5d4f..7359273 100644
--- a/include/m908/getters.cpp
+++ b/include/m908/getters.cpp
@@ -70,7 +70,8 @@ bool mouse_m908::get_detach_kernel_driver(){
 
 int mouse_m908::get_key_mapping_raw( mouse_m908::rd_profile profile, int key, std::array<uint8_t, 4>& mapping ){
 	
-	if( key < 0 || key > 19 ) // valid key ?
+	// valid key ?
+	if( _c_button_names[key] == "" )
 		return 1;
 	
 	mapping[0] = _s_keymap_data[profile][key][0];
@@ -83,7 +84,8 @@ int mouse_m908::get_key_mapping_raw( mouse_m908::rd_profile profile, int key, st
 
 int mouse_m908::get_key_mapping( mouse_m908::rd_profile profile, int key, std::string& mapping ){
 	
-	if( key < 0 || key > 19 ) // valid key ?
+	// valid key ?
+	if( _c_button_names[key] == "" )
 		return 1;
 	
 	uint8_t b1 = _s_keymap_data[profile][key][0];
diff --git a/include/rd_mouse.h b/include/rd_mouse.h
index d126081..ad1cbf4 100644
--- a/include/rd_mouse.h
+++ b/include/rd_mouse.h
@@ -93,7 +93,7 @@ class rd_mouse{
 		
 };
 
-// include header files for the individual models TODO!
+// include header files for the individual models
 #include "m908/mouse_m908.h"
 #include "m709/mouse_m709.h"