diff --git a/build/mac/BuildList.pm b/build/mac/BuildList.pm
index edd1aca84650..d3dbb550a8f4 100644
--- a/build/mac/BuildList.pm
+++ b/build/mac/BuildList.pm
@@ -4,7 +4,7 @@ package			BuildList;
 require			Exporter;
 
 @ISA				= qw(Exporter);
-@EXPORT			= qw(BuildMozilla DistMozilla);
+@EXPORT			= qw(BuildMozilla DistMozilla SetBuildNumber);
 
 =head1 NAME
 
@@ -48,7 +48,7 @@ sub BuildMozilla()
 				$D = "";
 				$dist_dir = ":mozilla:dist:client:";
 			}
-		
+
 			#
 			# Build the appropriate target of each project
 			#
@@ -341,5 +341,23 @@ sub DistMozilla()
 		InstallFromManifest(":mozilla:base:src:MANIFEST",								":mozilla:dist:base:");
 	}
 
+ sub SetBuildNumber
+ {
+
+   open (OUTPUT, ">:mozilla:config:build_number") || die "could not open buildnumber";
+
+   open (BDATE, "perl :mozilla:config:bdate.pl|");
+   
+   while (<BDATE>) {
+     print OUTPUT $_;
+   }
+
+   close (BDATE);
+   close (OUTPUT);
+
+   system ("perl :mozilla:config:aboutime.pl :mozilla:l10n:us:xp:about-all.html :mozilla:config:build_number");
+
+ }
+
 1;
 
diff --git a/build/mac/BuildMozillaDebug.pl b/build/mac/BuildMozillaDebug.pl
index 03b3a300c0c6..9cb5c1dd5f9e 100644
--- a/build/mac/BuildMozillaDebug.pl
+++ b/build/mac/BuildMozillaDebug.pl
@@ -36,5 +36,7 @@ chdir("::::");
 # Make and popuplate the dist directory
 DistMozilla();
 
+SetBuildNumber();
+
 # Now build the projects
 BuildMozilla();