diff --git a/admin.php b/admin.php
index 0145d2a..0eddd5d 100644
--- a/admin.php
+++ b/admin.php
@@ -368,9 +368,10 @@ function bpges_install_queued_items_table() {
 				type varchar(75) NOT NULL,
 				date_recorded datetime NOT NULL default '0000-00-00 00:00:00',
 				KEY user_id (user_id),
-				KEY group_id (user_id),
+				KEY group_id (group_id),
 				KEY activity_id (activity_id),
-				KEY user_group_type_date (user_id,type,date_recorded)
+				KEY user_group_type_date (user_id,type,date_recorded),
+				UNIQUE KEY user_group_activity_type (user_id,group_id,activity_id,type)
 			) {$charset_collate};";
 
 	dbDelta( $sql );
diff --git a/classes/class-bpges-queued-item.php b/classes/class-bpges-queued-item.php
index 030ef82..bad930d 100644
--- a/classes/class-bpges-queued-item.php
+++ b/classes/class-bpges-queued-item.php
@@ -60,7 +60,7 @@ public static function bulk_insert( $data ) {
 
 		$table_name = self::get_table_name();
 		$values_sql = implode( ', ', $values );
-		$sql = "INSERT INTO {$table_name} (user_id, group_id, activity_id, type, date_recorded) VALUES {$values_sql}";
+		$sql = "INSERT IGNORE INTO {$table_name} (user_id, group_id, activity_id, type, date_recorded) VALUES {$values_sql}";
 		return $wpdb->query( $sql );
 	}
 
diff --git a/tests/testcases/subscription.php b/tests/testcases/subscription.php
index 8e4ab7d..60f9f85 100644
--- a/tests/testcases/subscription.php
+++ b/tests/testcases/subscription.php
@@ -57,4 +57,34 @@ public function test_digest_record_activity() {
 
 		$this->assertSame( $expected, $queue );
 	}
+
+	public function test_record_duplicate_activity_should_not_be_allowed() {
+		$activity_id = 123;
+
+		$activity = array(
+			'user_id'       => self::$user_ids[0],
+			'group_id'      => self::$group_ids[0],
+			'activity_id'   => $activity_id,
+			'type'          => 'immediate',
+			'date_recorded' => date( 'Y-m-d H:i:s', time() - 3600 ),
+		);
+
+		// Add the item to the queue.
+		$add = array( $activity );
+		BPGES_Queued_Item::bulk_insert( $add );
+
+		// Add the same item to the queue with a slightly different date.
+		$activity['date_recorded'] = date( 'Y-m-d H:i:s' );
+		$add = array( $activity );
+		BPGES_Queued_Item::bulk_insert( $add );
+
+		// Fetch queued items for our group.
+		$sub = new BPGES_Queued_Item_Query( array(
+			'group_id' => self::$group_ids[0],
+		) );
+		$sub = $sub->get_results();
+
+		// Assert that only 1 item was added to the queued items DB table.
+		$this->assertSame( 1, count( $sub ) );
+	}
 }