diff --git a/stoneridge.py b/stoneridge.py
index b60adb6..a0ee6f6 100644
--- a/stoneridge.py
+++ b/stoneridge.py
@@ -27,6 +27,7 @@ os_version = None
 download_platform = None
 download_suffix = None
 current_netconfig = None
+buildid_suffix = None
 
 # Paths that multiple programs need to know about
 installroot = None
@@ -269,6 +270,18 @@ def setup_dirnames(srroot, srwork, srxpcout):
         # don't worry if we can't get it earlier in the process
         pass
 
+_netconfig_ids = {
+    'broadband':'0',
+    'umts':'1',
+    'gsm':'2',
+}
+
+_os_ids = {
+    'windows':'w',
+    'linux':'l',
+    'mac':'m',
+}
+
 class ArgumentParser(argparse.ArgumentParser):
     """An argument parser for stone ridge programs that handles the arguments
     required by all of them
@@ -290,6 +303,7 @@ class ArgumentParser(argparse.ArgumentParser):
     def parse_args(self, **kwargs):
         global _conffile
         global current_netconfig
+        global buildid_suffix
 
         args = argparse.ArgumentParser.parse_args(self, **kwargs)
 
@@ -298,4 +312,6 @@ class ArgumentParser(argparse.ArgumentParser):
 
         setup_dirnames(args._sr_root_, args._sr_work_, args._sr_xpcout_)
 
+        buildid_suffix = _os_ids[os_name] + _netconfig_ids[current_netconfig]
+
         return args
diff --git a/stoneridge_info_gatherer.py b/stoneridge_info_gatherer.py
index bee5875..ad1595f 100644
--- a/stoneridge_info_gatherer.py
+++ b/stoneridge_info_gatherer.py
@@ -27,14 +27,16 @@ class StoneRidgeInfoGatherer(object):
         build_info['branch'] = stoneridge.current_netconfig
 
         # Due to the way the graph server works, we need to create a unique
-        # build id for each build/netconfig combination. We also want to keep
+        # build id for each build/os/netconfig combination. We also want to keep
         # the unmodified build ID around for posterity.
         build_info['original_buildid'] = cp.get('App', 'BuildID')
-        # Cut off the century and the seconds from the date in the build id, as
-        # they are relatively useless bits of information.
-        buildid_base = build_info['original_buildid'][2:-2]
-        # Build ID is limited to 16 characters in the receiving database.
-        build_info['id'] = (buildid_base + stoneridge.current_netconfig)[:16]
+
+        # Build ID is limited to 16 characters in the receiving database, and
+        # our suffix is 2 characters, so we truncate the original to 14
+        # characters before adding our suffix. It should already be only 14
+        # characters, but we do this Just In Case.
+        buildid_base = build_info['original_buildid'][:14]
+        build_info['id'] = buildid_base + stoneridge.buildid_suffix
 
         machine_info = {}
         machine_info['name'] = platform.node()
diff --git a/tools/fix_buildids.py b/tools/fix_buildids.py
index d5639d9..3bb6371 100644
--- a/tools/fix_buildids.py
+++ b/tools/fix_buildids.py
@@ -31,8 +31,11 @@ for fname in sys.argv[1:]:
 
     # See stoneridge_info_gatherer.py for why the buildid is the way it is.
     netconfig = info['test_build']['branch']
+    os_name = info['test_machine']['os']
+    buildid_suffix = (stoneridge._os_ids[os_name] +
+                      stoneridge._netconfig_ids[netconfig])
     original_buildid = info['test_build']['id']
-    new_buildid = (original_buildid[2:-2] + netconfig)[:16]
+    new_buildid = original_buildid[:14] + buildid_suffix
 
     info['test_build']['original_buildid'] = original_buildid
     info['test_build']['id'] = new_buildid