diff --git a/src/window.py b/src/window.py
index c05c6f6..db3f7df 100644
--- a/src/window.py
+++ b/src/window.py
@@ -29,6 +29,7 @@ class LumosWindow(Adw.ApplicationWindow):
     lux_label = Gtk.Template.Child()
     ev_label = Gtk.Template.Child()
     error_banner = Gtk.Template.Child()
+    sensor_unit_error_banner = Gtk.Template.Child()
 
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
@@ -49,9 +50,15 @@ class LumosWindow(Adw.ApplicationWindow):
 
     def onSensorRead(self, value: float, unit: str):
         # Called when the light value changed
+
         if self.lux_label:
             self.lux_label.set_label("{:.0f} {}".format(value, unit))
 
+        # Check the unit is absolute ("lux"), otherwise there's no way to convert to an absolute EV value
+        if unit != "lux":
+            self.sensor_unit_error_banner.set_revealed(True)
+            return
+
         # Convert lux to EV
         ev = EVCalculator.luxToEV(value)
         if self.ev_label:
diff --git a/src/window.ui b/src/window.ui
index 46b7c8a..e47551c 100644
--- a/src/window.ui
+++ b/src/window.ui
@@ -51,6 +51,12 @@
                 <signal name="button-clicked" handler="showErrorDetails"/>"
               </object>
             </child>
+            <child>
+              <object class="AdwBanner" id="sensor_unit_error_banner">
+                <property name="title" translatable="true">Light sensor does not support absolute light measurement: unable to compute exposition</property>
+              </object>
+            </child>
+"
 
             <!-- Pages Stack -->
             <child>
@@ -127,7 +133,7 @@
                         </child>
                         <child>
                           <object class="GtkLabel" id="ev_label">
-                            <property name="label" translatable="no">XXX EV</property>
+                            <property name="label" translatable="no">-- EV</property>
                             <style>
                               <class name="title-1"/>
                             </style>