diff --git a/dtool/src/prc/configPage.cxx b/dtool/src/prc/configPage.cxx
index b8acfa879a..1059f2ea46 100644
--- a/dtool/src/prc/configPage.cxx
+++ b/dtool/src/prc/configPage.cxx
@@ -153,7 +153,7 @@ read_prc(istream &in) {
 
     // Look for the first line in the buffer..
     char *newline = (char *)memchr((void *)buffer, '\n', count);
-    if (newline == NULL) {
+    if (newline == (char *)NULL) {
       // The buffer was one long line.  Huh.
       prev_line += string(buffer, count);
 
@@ -165,7 +165,7 @@ read_prc(istream &in) {
       // Now look for the next line, etc.
       char *start = newline + 1;
       newline = (char *)memchr((void *)start, '\n', buffer_end - start);
-      while (newline != NULL) {
+      while (newline != (char *)NULL) {
         length = newline - start;
         read_prc_line(string(start, length + 1));
         start = newline + 1;
@@ -290,7 +290,7 @@ get_num_declarations() const {
 ////////////////////////////////////////////////////////////////////
 const ConfigDeclaration *ConfigPage::
 get_declaration(int n) const {
-  nassertr(n >= 0 && n < (int)_declarations.size(), NULL);
+  nassertr(n >= 0 && n < (int)_declarations.size(), (ConfigDeclaration *)NULL);
   return _declarations[n];
 }
 
diff --git a/dtool/src/prc/configPageManager.I b/dtool/src/prc/configPageManager.I
index 451ed77b48..e4ccb8044d 100644
--- a/dtool/src/prc/configPageManager.I
+++ b/dtool/src/prc/configPageManager.I
@@ -137,7 +137,7 @@ get_num_implicit_pages() const {
 INLINE ConfigPage *ConfigPageManager::
 get_implicit_page(int n) const {
   check_sort_pages();
-  nassertr(n >= 0 && n < (int)_implicit_pages.size(), NULL);
+  nassertr(n >= 0 && n < (int)_implicit_pages.size(), (ConfigPage *)NULL);
   return _implicit_pages[n];
 }
 
@@ -163,7 +163,7 @@ get_num_explicit_pages() const {
 INLINE ConfigPage *ConfigPageManager::
 get_explicit_page(int n) const {
   check_sort_pages();
-  nassertr(n >= 0 && n < (int)_explicit_pages.size(), NULL);
+  nassertr(n >= 0 && n < (int)_explicit_pages.size(), (ConfigPage *)NULL);
   return _explicit_pages[n];
 }
 
diff --git a/dtool/src/prc/configVariableCore.I b/dtool/src/prc/configVariableCore.I
index d6a27f42a6..4b105b7e1e 100644
--- a/dtool/src/prc/configVariableCore.I
+++ b/dtool/src/prc/configVariableCore.I
@@ -204,7 +204,7 @@ get_num_references() const {
 INLINE const ConfigDeclaration *ConfigVariableCore::
 get_reference(int n) const {
   check_sort_declarations();
-  nassertr(n >= 0 && n < (int)_declarations.size(), NULL);
+  nassertr(n >= 0 && n < (int)_declarations.size(), (ConfigDeclaration *)NULL);
   return _declarations[n];
 }
 
@@ -238,7 +238,7 @@ get_num_trusted_references() const {
 INLINE const ConfigDeclaration *ConfigVariableCore::
 get_trusted_reference(int n) const {
   check_sort_declarations();
-  nassertr(n >= 0 && n < (int)_trusted_declarations.size(), NULL);
+  nassertr(n >= 0 && n < (int)_trusted_declarations.size(), (ConfigDeclaration *)NULL);
   return _trusted_declarations[n];
 }
 
@@ -265,7 +265,7 @@ get_num_unique_references() const {
 INLINE const ConfigDeclaration *ConfigVariableCore::
 get_unique_reference(int n) const {
   check_sort_declarations();
-  nassertr(n >= 0 && n < (int)_unique_declarations.size(), NULL);
+  nassertr(n >= 0 && n < (int)_unique_declarations.size(), (ConfigDeclaration *)NULL);
   return _unique_declarations[n];
 }
 
diff --git a/dtool/src/prc/configVariableCore.cxx b/dtool/src/prc/configVariableCore.cxx
index 8c730b784c..43cb14e532 100644
--- a/dtool/src/prc/configVariableCore.cxx
+++ b/dtool/src/prc/configVariableCore.cxx
@@ -246,7 +246,7 @@ bool ConfigVariableCore::
 clear_local_value() {
   if (_local_value != (ConfigDeclaration *)NULL) {
     ConfigPage::get_local_page()->delete_declaration(_local_value);
-    _local_value = NULL;
+    _local_value = (ConfigDeclaration *)NULL;
     _value_seq++;
     return true;
   }
diff --git a/dtool/src/prc/configVariableManager.I b/dtool/src/prc/configVariableManager.I
index 85de8f4ba7..5c03e21b0f 100644
--- a/dtool/src/prc/configVariableManager.I
+++ b/dtool/src/prc/configVariableManager.I
@@ -35,7 +35,7 @@ get_num_variables() const {
 ////////////////////////////////////////////////////////////////////
 INLINE ConfigVariableCore *ConfigVariableManager::
 get_variable(int n) const {
-  nassertr(n >= 0 && n < (int)_variables.size(), NULL);
+  nassertr(n >= 0 && n < (int)_variables.size(), (ConfigVariableCore *)NULL);
   return _variables[n];
 }
 
diff --git a/dtool/src/prc/notify.cxx b/dtool/src/prc/notify.cxx
index 489e6df468..fb65a8c970 100644
--- a/dtool/src/prc/notify.cxx
+++ b/dtool/src/prc/notify.cxx
@@ -253,7 +253,7 @@ get_top_category() {
 NotifyCategory *Notify::
 get_category(const string &basename, NotifyCategory *parent_category) {
   // The string should not contain colons.
-  nassertr(basename.find(':') == string::npos, NULL);
+  nassertr(basename.find(':') == string::npos, (NotifyCategory *)NULL);
 
   string fullname;
   if (parent_category != (NotifyCategory *)NULL) {
@@ -270,7 +270,7 @@ get_category(const string &basename, NotifyCategory *parent_category) {
   }
 
   pair<Categories::iterator, bool> result = 
-    _categories.insert(Categories::value_type(fullname, NULL));
+    _categories.insert(Categories::value_type(fullname, (NotifyCategory *)NULL));
 
   bool inserted = result.second;
   NotifyCategory *&category = (*result.first).second;
diff --git a/dtool/src/prc/prcKeyRegistry.cxx b/dtool/src/prc/prcKeyRegistry.cxx
index 7b597bc931..56442c6efc 100644
--- a/dtool/src/prc/prcKeyRegistry.cxx
+++ b/dtool/src/prc/prcKeyRegistry.cxx
@@ -66,7 +66,7 @@ void PrcKeyRegistry::
 record_keys(const KeyDef *key_def, int num_keys) {
   for (int i = 0; i < num_keys; i++) {
     const KeyDef *def = &key_def[i];
-    if (def->_data != NULL) {
+    if (def->_data != (char *)NULL) {
       // Clear the ith key.
       while ((int)_keys.size() <= i) {
         Key key;
@@ -136,7 +136,7 @@ get_num_keys() const {
 ////////////////////////////////////////////////////////////////////
 EVP_PKEY *PrcKeyRegistry::
 get_key(int n) const {
-  nassertr(n >= 0 && n < (int)_keys.size(), NULL);
+  nassertr(n >= 0 && n < (int)_keys.size(), (EVP_PKEY *)NULL);
 
   if (_keys[n]._def != (KeyDef *)NULL) {
     if (_keys[n]._pkey == (EVP_PKEY *)NULL) {