diff --git a/app/public/assets/css/common.css b/app/public/assets/css/common.css
index 2e4fc78..860ef72 100644
--- a/app/public/assets/css/common.css
+++ b/app/public/assets/css/common.css
@@ -134,7 +134,7 @@ header {
 
   /* nav-mobile-links: mobile-only dropdown, hidden at desktop */
   .nav-mobile-links {
-    display: none;
+    display: none; /* overridden to block inside the mobile media query */
   }
 }
 
@@ -227,8 +227,9 @@ header {
     display: flex;
   }
 
-  /* Dropdown: clipped by default */
+  /* Dropdown: shown as block but clipped to zero height by default */
   header nav[aria-label="Navigation principale"] .nav-mobile-links {
+    display: block; /* override the desktop display:none */
     list-style: none;
     margin: 0;
     padding: 0;