diff --git a/modules/book/book.module b/modules/book/book.module
index 966330b373ae930b639af82a504b99060775d75e..56f839a33c64f76d2be660bcb696d435190ae84b 100644
--- a/modules/book/book.module
+++ b/modules/book/book.module
@@ -649,7 +649,7 @@ function book_build_active_trail($book_link) {
  * Appends book navigation to all nodes in the book, and handles book outline
  * insertions and updates via the node form.
  */
-function book_nodeapi(&$node, $op, $teaser, $page) {
+function book_nodeapi(&$node, $op, $teaser = NULL, $page = NULL) {
   switch ($op) {
     case 'load':
       // Note - we cannot use book_link_load() because it will call node_load()
diff --git a/modules/forum/forum.module b/modules/forum/forum.module
index 1d8f4a48d181599397145a42e397639a4c3bf6f0..1b027f3d224a9c5c79e2ab7e30fc242815985067 100644
--- a/modules/forum/forum.module
+++ b/modules/forum/forum.module
@@ -165,7 +165,7 @@ function forum_init() {
 /**
  * Implementation of hook_nodeapi().
  */
-function forum_nodeapi(&$node, $op, $teaser, $page) {
+function forum_nodeapi(&$node, $op, $teaser = NULL, $page = NULL) {
   // We are going to return if $node->type is not one of the node
   // types assigned to the forum vocabulary.  If forum_nav_vocabulary
   // is undefined or the vocabulary does not exist, it clearly cannot
diff --git a/modules/path/path.module b/modules/path/path.module
index a267fd6df63a0f71ea1fa5f77eab4dc03d892fef..67fabbcc92f407c6f15636044446c048a21d95d6 100644
--- a/modules/path/path.module
+++ b/modules/path/path.module
@@ -130,7 +130,7 @@ function path_set_alias($path = NULL, $alias = NULL, $pid = NULL, $language = ''
  * Allows URL aliases for nodes to be specified at node edit time rather
  * than through the administrative interface.
  */
-function path_nodeapi(&$node, $op, $arg) {
+function path_nodeapi(&$node, $op, $arg = NULL) {
   // Permissions are required for everything except node loading.
   if (user_access('create url aliases') || user_access('administer url aliases') || ($op == 'load')) {
     $language = isset($node->language) ? $node->language : '';
diff --git a/modules/translation/translation.module b/modules/translation/translation.module
index a701e1a8a72abe9b25d4947a4409a35c2a22b7ea..cf17cd15c8673ea1e34ce19c30fbc501daef2ab1 100644
--- a/modules/translation/translation.module
+++ b/modules/translation/translation.module
@@ -180,7 +180,7 @@ function translation_link($type, $node = NULL, $teaser = FALSE) {
  *
  * Manages translation information for nodes.
  */
-function translation_nodeapi(&$node, $op, $teaser, $page) {
+function translation_nodeapi(&$node, $op, $teaser = NULL, $page = NULL) {
   // Only act if we are dealing with a content type supporting translations.
   if (!translation_supported_type($node->type)) {
     return;
diff --git a/modules/trigger/trigger.module b/modules/trigger/trigger.module
index 7c7ff4b3c7d4ce9eed46217dd09bb7a5abc64cdc..263a2a125ba61044b06e5bafb1512914a589d3ff 100644
--- a/modules/trigger/trigger.module
+++ b/modules/trigger/trigger.module
@@ -210,7 +210,7 @@ function _trigger_normalize_node_context($type, $node) {
 /**
  * Implementation of hook_nodeapi().
  */
-function trigger_nodeapi(&$node, $op, $a3, $a4) {
+function trigger_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL) {
   // Keep objects for reuse so that changes actions make to objects can persist.
   static $objects;
   // Prevent recursion by tracking which operations have already been called.
diff --git a/modules/upload/upload.module b/modules/upload/upload.module
index 3212ce9ec375f1bbb9ad732d8698bdbcec67cc3b..3a9e973c3cab5a0b3a67c1b4cb34564e671ea394 100644
--- a/modules/upload/upload.module
+++ b/modules/upload/upload.module
@@ -272,7 +272,7 @@ function upload_form_alter(&$form, $form_state, $form_id) {
 /**
  * Implementation of hook_nodeapi().
  */
-function upload_nodeapi(&$node, $op, $teaser) {
+function upload_nodeapi(&$node, $op, $teaser = NULL) {
   switch ($op) {
 
     case 'load':