diff --git a/dtool/pptempl/Template.unix.pp b/dtool/pptempl/Template.unix.pp
index b3cd31d4b5..e092720fac 100644
--- a/dtool/pptempl/Template.unix.pp
+++ b/dtool/pptempl/Template.unix.pp
@@ -179,6 +179,23 @@ cleanall : clean
 	rm -f $[DEPENDENCY_CACHE_FILENAME]
 #endif
 
+clean-igate :
+#forscopes metalib_target lib_target ss_lib_target
+  #define igatedb $[get_igatedb]
+  #define igateoutput $[get_igateoutput]
+  #define igatemscan $[components $[get_igatedb:%=$[RELDIR]/$[so_dir]/%],$[active_component_libs]]
+  #define igatemout $[if $[igatemscan],lib$[TARGET]_module.cxx]
+  #if $[igatedb]
+	rm -f $[so_dir]/$[igatedb]
+  #endif
+  #if $[igateoutput]
+	rm -f $[so_dir]/$[igateoutput] $[igateoutput:%.cxx=$[so_dir]/%.o]
+  #endif
+  #if $[igatemout]
+	rm -f $[so_dir]/$[igatemout] $[igatemout:%.cxx=$[so_dir]/%.o]
+  #endif
+#end metalib_target lib_target ss_lib_target
+
 // Now, 'install' and 'uninstall'.  These simply copy files into the
 // install directory (or remove them).  The 'install' rule also makes
 // the directories if necessary.
@@ -189,6 +206,9 @@ cleanall : clean
      $[INSTALL_DATA:%=$[install_data_dir]/%] \
      $[INSTALL_CONFIG:%=$[install_config_dir]/%]
 
+#define installed_igate_files \
+     $[get_igatedb(metalib_target lib_target ss_lib_target):%=$[install_igatedb_dir]/%]
+
 #define install_targets \
      $[sort \
        $[if $[install_lib],$[install_lib_dir]] \
@@ -204,11 +224,18 @@ cleanall : clean
      $[installed_files]
 install : all $[install_targets]
 
+install-igate : $[sort $[installed_igate_files]]
+
 uninstall : $[TARGET(metalib_target lib_target ss_lib_target static_lib_target):%=uninstall-lib%] $[TARGET(bin_target):%=uninstall-%]
 #if $[installed_files]
 	rm -f $[sort $[installed_files]]
 #endif
 
+uninstall-igate :
+#if $[installed_igate_files]
+	rm -f $[sort $[installed_igate_files]]
+#endif
+
 
 // We need a rule for each directory we might need to make.  This
 // loops through the full set of directories and creates a rule to
@@ -737,12 +764,15 @@ $[DEPENDENCY_CACHE_FILENAME] : $[dep_sources]
 all : $[subdirs]
 test : $[subdirs:%=test-%]
 clean : $[subdirs:%=clean-%]
+clean-igate : $[subdirs:%=clean-igate-%]
 cleanall : $[subdirs:%=cleanall-%]
 install : $[if $[CONFIG_HEADER],$[install_headers_dir] $[install_headers_dir]/$[CONFIG_HEADER]] $[subdirs:%=install-%]
+install-igate : $[subdirs:%=install-igate-%]
 uninstall : $[subdirs:%=uninstall-%]
 #if $[CONFIG_HEADER]
 	rm -f $[install_headers_dir]/$[CONFIG_HEADER]
 #endif
+uninstall-igate : $[subdirs:%=uninstall-igate-%]
 
 // Somehow, something in the cttools confuses some shells, so that
 // when we are attached, 'cd foo' doesn't work, but 'cd ./foo' does.
@@ -765,6 +795,11 @@ clean-$[dirname] :
 	cd ./$[PATH]; $(MAKE) clean
 #end dirname
 
+#formap dirname subdirs
+clean-igate-$[dirname] :
+	cd ./$[PATH]; $(MAKE) clean-igate
+#end dirname
+
 #formap dirname subdirs
 cleanall-$[dirname] : $[patsubst %,cleanall-%,$[dirnames $[if $[build_directory],$[DIRNAME]],$[DEPEND_DIRS]]]
 	cd ./$[PATH]; $(MAKE) cleanall
@@ -775,11 +810,21 @@ install-$[dirname] : $[patsubst %,install-%,$[dirnames $[if $[build_directory],$
 	cd ./$[PATH]; $(MAKE) install
 #end dirname
 
+#formap dirname subdirs
+install-igate-$[dirname] :
+	cd ./$[PATH]; $(MAKE) install-igate
+#end dirname
+
 #formap dirname subdirs
 uninstall-$[dirname] :
 	cd ./$[PATH]; $(MAKE) uninstall
 #end dirname
 
+#formap dirname subdirs
+uninstall-igate-$[dirname] :
+	cd ./$[PATH]; $(MAKE) uninstall-igate
+#end dirname
+
 #if $[ne $[CONFIG_HEADER],]
 $[install_headers_dir] :
 	@test -d $[install_headers_dir] || echo mkdir -p $[install_headers_dir]
diff --git a/dtool/src/interrogate/interrogate.cxx b/dtool/src/interrogate/interrogate.cxx
index ddb4c4788f..842ac6761e 100644
--- a/dtool/src/interrogate/interrogate.cxx
+++ b/dtool/src/interrogate/interrogate.cxx
@@ -36,6 +36,7 @@ bool build_python_wrappers = false;
 bool save_unique_names = false;
 bool no_database = false;
 bool generate_spam = false;
+bool left_inheritance_requires_upcast = false;
 CPPVisibility min_vis = V_published;
 string library_name;
 string module_name;
diff --git a/dtool/src/interrogate/interrogate.h b/dtool/src/interrogate/interrogate.h
index 494cbdcb00..2034bf2d45 100644
--- a/dtool/src/interrogate/interrogate.h
+++ b/dtool/src/interrogate/interrogate.h
@@ -30,6 +30,7 @@ extern bool build_python_wrappers;
 extern bool save_unique_names;
 extern bool no_database;
 extern bool generate_spam;
+extern bool left_inheritance_requires_upcast;
 extern CPPVisibility min_vis;
 extern string library_name;
 extern string module_name;
diff --git a/dtool/src/interrogate/interrogateBuilder.cxx b/dtool/src/interrogate/interrogateBuilder.cxx
index 4221aa881d..8406f8028e 100644
--- a/dtool/src/interrogate/interrogateBuilder.cxx
+++ b/dtool/src/interrogate/interrogateBuilder.cxx
@@ -2003,21 +2003,6 @@ define_struct_type(InterrogateType &itype, CPPStructType *cpptype,
   itype._flags |= InterrogateType::F_global;
 
   CPPScope *scope = cpptype->_scope;
-      
-  // Record the derivation of this class.  Do we need to synthesize
-  // upcast/downcast functions?
-  bool generate_casts = false;
-  if (cpptype->_derivation.size() > 1) {
-    // If we have multiple inheritance, we need explicit cast operators.
-    generate_casts = true;
-  }
-  if (cpptype->_derivation.size() == 1) {
-    // If we have single inheritance, but it's a virtual inheritance,
-    // we also need explicit cast operators.
-    if (cpptype->_derivation.front()._is_virtual) {
-      generate_casts = true;
-    }
-  }
 
   CPPStructType::Derivation::const_iterator bi;
   for (bi = cpptype->_derivation.begin();
@@ -2033,12 +2018,32 @@ define_struct_type(InterrogateType &itype, CPPStructType *cpptype,
       d._base = base_index;
       d._upcast = 0;
       d._downcast = 0;
+
+      // Do we need to synthesize upcast and downcast functions?
+      bool generate_casts = false;
+      if (base._is_virtual) {
+	// We do in the presence of virtual inheritance.
+	generate_casts = true;
+
+      } else if (bi != cpptype->_derivation.begin()) {
+	// Or if we're not talking about the leftmost fork of multiple
+	// inheritance.
+	generate_casts = true;
+
+      } else if (cpptype->_derivation.size() != 1 &&
+		 left_inheritance_requires_upcast) {
+	// Or even if we are the leftmost fork of multiple
+	// inheritance, if the flag is set indicating that this
+	// requires a pointer change.  (For most compilers, this does
+	// not require a pointer change.)
+	generate_casts = true;
+      }
       
       if (generate_casts) {
 	d._upcast = get_cast_function(base_type, cpptype, "upcast");
 	d._flags |= InterrogateType::DF_upcast;
 
-	if ((*bi)._is_virtual) {
+	if (base._is_virtual) {
 	  // If this is a virtual inheritance, we can't write a
 	  // downcast.
 	  d._flags |= InterrogateType::DF_downcast_impossible;