diff -u b/restrict_ip.install b/restrict_ip.install
--- b/restrict_ip.install
+++ b/restrict_ip.install
@@ -115,3 +115,17 @@
     ],
   ]);
 }
+
+/**
+ * Add primary keys for "restrict_ip_paths" and "restrict_ip_whitelisted_ip_addresses" tables.
+ */
+function restrict_ip_update_9401() {
+  // Add primary key to "restrict_ip_paths" table.
+  \Drupal::database()
+    ->schema()
+    ->addPrimaryKey('restrict_ip_paths', ['path']);
+  // Add primary key to "restrict_ip_whitelisted_ip_addresses" table.
+  \Drupal::database()
+    ->schema()
+    ->addPrimaryKey('restrict_ip_whitelisted_ip_addresses', ['ip_address']);
+}