--- a/devtools/client/shared/widgets/filter-widget.css
+++ b/devtools/client/shared/widgets/filter-widget.css
@@ -132,16 +132,21 @@ html, body {
   margin-right: 10px;
   flex: 1;
 }
 
 .filter-value input {
   flex-grow: 1;
 }
 
+/* Fix the size of inputs */
+/* Especially needed on Linux where input are bigger */
+input {
+  width: 8em;
+}
 
 .theme-light .add,
 .theme-light .remove-button,
 .theme-light #toggle-presets {
   filter: invert(1);
 }
 
 .preset {