diff --git a/examples/us-terminal-with-scancodes/sq2lv_layouts.c b/examples/us-terminal-with-scancodes/sq2lv_layouts.c
index d4c20bf..73c8e42 100644
--- a/examples/us-terminal-with-scancodes/sq2lv_layouts.c
+++ b/examples/us-terminal-with-scancodes/sq2lv_layouts.c
@@ -24,7 +24,7 @@ static const char * const keycaps_lower_terminal_us[] = { \
 };
 
 static const lv_btnmatrix_ctrl_t attributes_lower_terminal_us[] = { \
-    LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
+    LV_KEYBOARD_CTRL_BTN_FLAGS | LV_BTNMATRIX_CTRL_CHECKABLE | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | LV_BTNMATRIX_CTRL_CHECKABLE | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
     2, 2, 2, 2, 2, 2, 2, 2, 2, \
     LV_KEYBOARD_CTRL_BTN_FLAGS | 3, 2, 2, 2, 2, 2, 2, 2, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
@@ -86,7 +86,7 @@ static const char * const keycaps_upper_terminal_us[] = { \
 };
 
 static const lv_btnmatrix_ctrl_t attributes_upper_terminal_us[] = { \
-    LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
+    LV_KEYBOARD_CTRL_BTN_FLAGS | LV_BTNMATRIX_CTRL_CHECKABLE | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | LV_BTNMATRIX_CTRL_CHECKABLE | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
     2, 2, 2, 2, 2, 2, 2, 2, 2, \
     LV_KEYBOARD_CTRL_BTN_FLAGS | 3, 2, 2, 2, 2, 2, 2, 2, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
@@ -148,7 +148,7 @@ static const char * const keycaps_numbers_terminal_us[] = { \
 };
 
 static const lv_btnmatrix_ctrl_t attributes_numbers_terminal_us[] = { \
-    LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
+    LV_KEYBOARD_CTRL_BTN_FLAGS | LV_BTNMATRIX_CTRL_CHECKABLE | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | LV_BTNMATRIX_CTRL_CHECKABLE | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
     2, 2, 2, 2, 2, 2, 2, LV_KEYBOARD_CTRL_BTN_FLAGS | 3, \
diff --git a/squeek2lvgl.py b/squeek2lvgl.py
index 8d3d05c..9d2c4b0 100644
--- a/squeek2lvgl.py
+++ b/squeek2lvgl.py
@@ -351,16 +351,37 @@ def key_to_keycap(key, view_id, layout_id):
     return keycap
 
 
+def key_is_modifier(key, data_buttons):
+    """Return true if a key acts as a modifier..
+
+    key -- the key in question
+    data_buttons -- the "buttons" object from the layout's YAML file
+    """
+    return key in data_buttons and 'modifier' in data_buttons[key]
+
+
 def key_to_attributes(key, data_buttons):
     """Return the LVGL button attributes for a key.
     
     key -- the key in question
     data_buttons -- the "buttons" object from the layout's YAML file
     """
-    if key in ['period', 'colon', '"'] or key not in data_buttons:
-        return '2'
-    width = 7 if key == 'space' else 3
-    return f'LV_KEYBOARD_CTRL_BTN_FLAGS | {width}'
+    attributes = []
+
+    if key in data_buttons and key not in ['period', 'colon', '"']:
+        attributes.append('LV_KEYBOARD_CTRL_BTN_FLAGS')
+
+    if key_is_modifier(key, data_buttons):
+        attributes.append('LV_BTNMATRIX_CTRL_CHECKABLE')
+
+    if key not in data_buttons or key in ['period', 'colon', '"']:
+        attributes.append('2')
+    elif key == 'space':
+        attributes.append('7')
+    else:
+        attributes.append('3')
+
+    return ' | '.join(attributes)
 
 
 def keycap_to_c_value(keycap):
@@ -523,7 +544,7 @@ def get_keycaps_attrs_modifiers_switchers_scancodes(args, layout_id, view_id, da
             keycaps_in_row.append(keycap_to_c_value(keycap))
             attrs_in_row.append(key_to_attributes(key, data_buttons))
 
-            if key in data_buttons and 'modifier' in data_buttons[key]:
+            if key_is_modifier(key, data_buttons):
                 modifier_idxs.append(idx)
 
             if key in data_buttons and 'action' in data_buttons[key]: