--- a/python/mozbuild/mozbuild/compilation/database.py
+++ b/python/mozbuild/mozbuild/compilation/database.py
@@ -11,16 +11,17 @@ from mozbuild.compilation import util
 from mozbuild.backend.common import CommonBackend
 from mozbuild.frontend.data import (
     Sources,
     GeneratedSources,
     DirectoryTraversal,
     Defines,
     Linkable,
     LocalInclude,
+    PerSourceFlag,
     VariablePassthru,
     SimpleProgram,
 )
 from mozbuild.shellutil import (
     quote as shell_quote,
 )
 from mozbuild.util import expand_variables
 import mozpack.path as mozpath
@@ -41,16 +42,17 @@ class CompileDBBackend(CommonBackend):
 
         # The cache for per-directory flags
         self._flags = {}
 
         self._envs = {}
         self._includes = defaultdict(list)
         self._defines = defaultdict(list)
         self._local_flags = defaultdict(dict)
+        self._per_source_flags = defaultdict(list)
         self._extra_includes = defaultdict(list)
         self._gyp_dirs = set()
         self._dist_include_testing = '-I%s' % mozpath.join(
             self.environment.topobjdir, 'dist', 'include', 'testing')
 
     def consume_object(self, obj):
         # Those are difficult directories, that will be handled later.
         if obj.relativedir in (
@@ -105,16 +107,19 @@ class CompileDBBackend(CommonBackend):
                     self._local_flags[obj.objdir][var] = obj.variables[var]
             if (obj.variables.get('DISABLE_STL_WRAPPING') and
                     'STL_FLAGS' in self._local_flags[obj.objdir]):
                 del self._local_flags[obj.objdir]['STL_FLAGS']
             if (obj.variables.get('ALLOW_COMPILER_WARNINGS') and
                     'WARNINGS_AS_ERRORS' in self._local_flags[obj.objdir]):
                 del self._local_flags[obj.objdir]['WARNINGS_AS_ERRORS']
 
+        elif isinstance(obj, PerSourceFlag):
+            self._per_source_flags[obj.file_name].extend(obj.flags)
+
         return True
 
     def consume_finished(self):
         CommonBackend.consume_finished(self)
 
         db = []
 
         for (directory, filename, unified), cmd in self._db.iteritems():
@@ -152,16 +157,19 @@ class CompileDBBackend(CommonBackend):
             for a in cmd:
                 a = expand_variables(a, variables).split()
                 if not a:
                     continue
                 if isinstance(a, types.StringTypes):
                     c.append(a)
                 else:
                     c.extend(a)
+            per_source_flags = self._per_source_flags.get(filename)
+            if per_source_flags is not None:
+                c.extend(per_source_flags)
             db.append({
                 'directory': directory,
                 'command': ' '.join(shell_quote(a) for a in c),
                 'file': filename,
             })
 
         import json
         # Output the database (a JSON file) to objdir/compile_commands.json