diff --git a/direct/src/p3d/PackageMerger.py b/direct/src/p3d/PackageMerger.py
index ac0c3f1b2f..505ae99dbb 100644
--- a/direct/src/p3d/PackageMerger.py
+++ b/direct/src/p3d/PackageMerger.py
@@ -136,9 +136,9 @@ class PackageMerger:
         self.contentsSeq = SeqValue()
 
         # We allow the first one to fail quietly.
-        self.__readContentsFile(self.installDir)
+        self.__readContentsFile(self.installDir, None)
 
-    def __readContentsFile(self, sourceDir):
+    def __readContentsFile(self, sourceDir, packageNames):
         """ Reads the contents.xml file from the indicated sourceDir,
         and updates the internal set of packages appropriately. """
 
@@ -170,10 +170,15 @@ class PackageMerger:
             xpackage = xcontents.FirstChildElement('package')
             while xpackage:
                 pe = self.PackageEntry(xpackage, sourceDir)
-                other = self.contents.get(pe.getKey(), None)
-                if not other or pe.isNewer(other):
-                    # Store this package in the resulting output.
-                    self.contents[pe.getKey()] = pe
+
+                # Filter out any packages not listed in
+                # packageNames (unless packageNames is None,
+                # in which case don't filter anything).
+                if packageNames is None or pe.packageName in packageNames:
+                    other = self.contents.get(pe.getKey(), None)
+                    if not other or pe.isNewer(other):
+                        # Store this package in the resulting output.
+                        self.contents[pe.getKey()] = pe
                     
                 xpackage = xpackage.NextSiblingElement('package')
 
@@ -268,10 +273,13 @@ class PackageMerger:
             except OSError:
                 pass
 
-    def merge(self, sourceDir):
+    def merge(self, sourceDir, packageNames = None):
         """ Adds the contents of the indicated source directory into
-        the current pool. """
-        if not self.__readContentsFile(sourceDir):
+        the current pool.  If packageNames is not None, it is a list
+        of package names that we wish to include from the source;
+        packages not named in this list will be unchanged. """
+        
+        if not self.__readContentsFile(sourceDir, packageNames):
             message = "Couldn't read %s" % (sourceDir)
             raise PackageMergerError, message            
 
diff --git a/direct/src/p3d/pmerge.py b/direct/src/p3d/pmerge.py
index 092cee0223..835cfcc5f3 100755
--- a/direct/src/p3d/pmerge.py
+++ b/direct/src/p3d/pmerge.py
@@ -30,6 +30,14 @@ Options:
      are checked for self-consistency with regards to hashes and
      timestamps.
 
+  -p packageName[,packageName...]
+     Specifies one or more particular packages by name that are to be
+     included from the input directories.  Any packages not in this
+     list are left unchanged in the install directory, even if there
+     is a newer version in one of the input directories.  If no
+     packages are named, all packages are involved.  This option may
+     be repeated.
+
   -h
      Display this help
 """
@@ -47,14 +55,17 @@ def usage(code, msg = ''):
     sys.exit(code)
 
 try:
-    opts, args = getopt.getopt(sys.argv[1:], 'i:h')
+    opts, args = getopt.getopt(sys.argv[1:], 'i:p:h')
 except getopt.error, msg:
     usage(1, msg)
 
 installDir = None
+packageNames = []
 for opt, arg in opts:
     if opt == '-i':
         installDir = Filename.fromOsSpecific(arg)
+    elif opt == '-p':
+        packageNames += arg.split(',')
         
     elif opt == '-h':
         usage(0)
@@ -62,6 +73,10 @@ for opt, arg in opts:
         print 'illegal option: ' + arg
         sys.exit(1)
 
+if not packageNames:
+    # No package names means allow all packages.
+    packageNames = None
+
 inputDirs = []
 for arg in args:
     inputDirs.append(Filename.fromOsSpecific(arg))
@@ -75,7 +90,7 @@ for arg in args:
 try:
     pm = PackageMerger.PackageMerger(installDir)
     for dir in inputDirs:
-        pm.merge(dir)
+        pm.merge(dir, packageNames = packageNames)
     pm.close()
         
 except PackageMerger.PackageMergerError: