diff --git a/mozilla/config/mddepend.pl b/mozilla/config/mddepend.pl
index 440ba5a6072..587497041eb 100644
--- a/mozilla/config/mddepend.pl
+++ b/mozilla/config/mddepend.pl
@@ -26,6 +26,8 @@
 #
 # Send comments, improvements, bugs to Steve Lamm (slamm@netscape.com).
 
+$outfile = shift @ARGV;
+
 @alldeps=();
 # Parse dependency files
 while ($line = <>) {
@@ -69,10 +71,27 @@ foreach $deps (@alldeps) {
       $modtimes{$dep_file} = $dep_mtime;
     }
     if ($dep_mtime eq '' or $dep_mtime > $mtime) {
-      print "$obj ";
-      $haveObjects = 1;
+      push @objs, $obj;
       last;
     }
   }
 }
-print ": FORCE\n" if $haveObjects;
+
+# Output objects to rebuild (if needed).
+if ($#objs > 0) {
+  $new_output = "@objs: FORCE\n";
+
+  # Read in the current dependencies file.
+  open(OLD, "<$outfile") and $old_output = <OLD>;
+  close(OLD);
+
+  # Only write out the dependencies if they are different.
+  if ($new_output ne $old_output) {
+    open(OUT, ">$outfile") and print OUT $new_output;
+    print "Updating dependencies ($outfile).\n";
+  }
+} elsif (-s $outfile) {
+  # Remove the old dependencies because all objects are up to date.
+  unlink $outfile;
+  print "Removing old dependencies ($outfile).\n";
+}
diff --git a/mozilla/config/rules.mk b/mozilla/config/rules.mk
index 8b365f41d53..75e15535871 100644
--- a/mozilla/config/rules.mk
+++ b/mozilla/config/rules.mk
@@ -1044,19 +1044,17 @@ endif # ! COMPILER_DEPEND
 # Yet another depend system: -MD
 ifdef COMPILER_DEPEND
 ifdef OBJS
-MDDEPEND_FILES := $(foreach obj, $(OBJS), \
-                    $(MDDEPDIR)/$(basename $(notdir $(obj))).pp)
-MDDEPEND_FILES := $(wildcard $(MDDEPEND_FILES))
+MDDEPEND_FILES := $(wildcard $(MDDEPDIR)/*.pp)
 ifdef MDDEPEND_FILES
 ifdef PERL
 # The script mddepend.pl checks the dependencies and writes to stdout
 # one rule to force out-of-date objects. For example,
 #   foo.o boo.o: FORCE
 # The script has an advantage over including the *.pp files directly
-# because it handles missing header files. 'make' would complain that
-# there is no way to build missing headers.
+# because it handles the case when header files are removed from the build.
+# 'make' would complain that there is no way to build missing headers.
 $(MDDEPDIR)/.all.pp: FORCE
-	@$(PERL) $(topsrcdir)/config/mddepend.pl $(MDDEPEND_FILES) >$@
+	@$(PERL) $(topsrcdir)/config/mddepend.pl $@ $(MDDEPEND_FILES) 
 -include $(MDDEPDIR)/.all.pp
 else
 include $(MDDEPEND_FILES)