diff --git a/course/social.php b/course/social.php
index f10c22fc360..47590113aec 100644
--- a/course/social.php
+++ b/course/social.php
@@ -2,8 +2,8 @@
     // social.php - course format featuring social forum
     //              included from view.php
     
-    include("../mod/forum/lib.php");
-    include("../mod/reading/lib.php"); 
+    include_once("../mod/forum/lib.php");
+    include_once("../mod/reading/lib.php"); 
 ?>
 
 <TABLE WIDTH="100%" BORDER="0" CELLSPACING="5" CELLPADDING="5">
diff --git a/course/topics.php b/course/topics.php
index a2b27856583..df1a8cc9866 100644
--- a/course/topics.php
+++ b/course/topics.php
@@ -6,7 +6,7 @@
       // courses that aren't so rigidly defined by time.
       // Included from "view.php"
 
-    include("../mod/forum/lib.php");
+    include_once("../mod/forum/lib.php");
 
     if (! $sections = get_all_sections($course->id) ) {
         $section->course = $course->id;   // Create a default section.
diff --git a/course/weeks.php b/course/weeks.php
index 49321c71ba0..80f2e06e532 100644
--- a/course/weeks.php
+++ b/course/weeks.php
@@ -2,7 +2,7 @@
       // Display the whole course as "weeks" made of of modules
       // Included from "view.php"
 
-    include("../mod/forum/lib.php");
+    include_once("../mod/forum/lib.php");
 
     if (! $sections = get_all_sections($course->id)) {
         $section->course = $course->id;   // Create a default section.