diff --git a/core/themes/seven/css/components/tables.css b/core/themes/seven/css/components/tables.css
index 90e7ac6690ba6103dc75f43db985745f05421017..727e0658e60174eae24225b2159e64f721ed5567 100644
--- a/core/themes/seven/css/components/tables.css
+++ b/core/themes/seven/css/components/tables.css
@@ -151,3 +151,12 @@ th.select-all {
     display: none;
   }
 }
+
+/**
+ * Target every .form-text input where its parent is a form-item inside a table
+ * cell.
+ */
+td > .form-item > .form-text,
+td > .ajax-new-content > .form-item > .form-text {
+  width: 100%;
+}