diff --git a/python/mozbuild/mozbuild/backend/recursivemake.py b/python/mozbuild/mozbuild/backend/recursivemake.py
index 7c9e4a0f618e..c8128e3349f9 100644
--- a/python/mozbuild/mozbuild/backend/recursivemake.py
+++ b/python/mozbuild/mozbuild/backend/recursivemake.py
@@ -16,6 +16,19 @@ from ..frontend.data import (
 from ..util import FileAvoidWrite
 
 
+STUB_MAKEFILE = '''
+# THIS FILE WAS AUTOMATICALLY GENERATED. DO NOT MODIFY BY HAND.
+
+DEPTH          := {depth}
+topsrcdir      := {topsrc}
+srcdir         := {src}
+VPATH          := {src}
+relativesrcdir := {relsrc}
+
+include {topsrc}/config/rules.mk
+'''.lstrip()
+
+
 class BackendMakeFile(object):
     """Represents a generated backend.mk file.
 
@@ -73,9 +86,17 @@ class BackendMakeFile(object):
         self.fh.write('\n')
         self.fh.write('MOZBUILD_DERIVED := 1\n')
 
-        # SUBSTITUTE_FILES handles Makefile.in -> Makefile conversion.
+        # SUBSTITUTE_FILES handles Makefile.in -> Makefile conversion. This
+        # also doubles to handle the case where there is no Makefile.in.
         self.fh.write('NO_MAKEFILE_RULE := 1\n')
 
+        # We can't blindly have a SUBMAKEFILES rule because some of the
+        # Makefile may not have a corresponding Makefile.in. For the case
+        # where a new directory is added, the mozbuild file referencing that
+        # new directory will need updated. This will cause a full backend
+        # scan and build, installing the new Makefile.
+        self.fh.write('NO_SUBMAKEFILES_RULE := 1\n')
+
 
     def write(self, buf):
         self.fh.write(buf)
@@ -157,16 +178,29 @@ class RecursiveMakeBackend(BuildBackend):
                 os.makedirs(bf.objdir)
 
             makefile_in = os.path.join(srcdir, 'Makefile.in')
+            makefile = os.path.join(bf.objdir, 'Makefile')
 
-            if not os.path.exists(makefile_in):
-                raise Exception('Could not find Makefile.in: %s' % makefile_in)
+            # If Makefile.in exists, use it as a template. Otherwise, create a
+            # stub.
+            if os.path.exists(makefile_in):
+                self.log(logging.DEBUG, 'substitute_makefile',
+                    {'path': makefile}, 'Substituting makefile: {path}')
+                bf.environment.create_config_file(makefile)
+                bf.write('SUBSTITUTE_FILES += Makefile\n')
+            else:
+                self.log(logging.DEBUG, 'stub_makefile',
+                    {'path': makefile}, 'Creating stub Makefile: {path}')
 
-            out_path = os.path.join(bf.objdir, 'Makefile')
-            self.log(logging.DEBUG, 'create_makefile', {'path': out_path},
-                'Generating makefile: {path}')
-            bf.environment.create_config_file(out_path)
+                params = {
+                    'topsrc': bf.environment.get_top_srcdir(makefile),
+                    'src': bf.environment.get_file_srcdir(makefile),
+                    'depth': bf.environment.get_depth(makefile),
+                    'relsrc': bf.environment.get_relative_srcdir(makefile),
+                }
+
+                with FileAvoidWrite(makefile) as fh:
+                    fh.write(STUB_MAKEFILE.format(**params))
 
-            bf.write('SUBSTITUTE_FILES += Makefile\n')
             bf.close()
 
     def _process_directory_traversal(self, obj, backend_file):
diff --git a/python/mozbuild/mozbuild/test/backend/data/stub0/dir2/Makefile.in b/python/mozbuild/mozbuild/test/backend/data/stub0/dir2/Makefile.in
deleted file mode 100644
index a038825a9429..000000000000
--- a/python/mozbuild/mozbuild/test/backend/data/stub0/dir2/Makefile.in
+++ /dev/null
@@ -1,12 +0,0 @@
-# Any copyright is dedicated to the Public Domain.
-# http://creativecommons.org/publicdomain/zero/1.0/
-
-DEPTH := @DEPTH@
-topsrcdir := @top_srcdir@
-srcdir := @srcdir@
-VPATH = @srcdir@
-
-include $(DEPTH)/config/autoconf.mk
-
-include $(topsrcdir)/config/rules.mk
-
diff --git a/python/mozbuild/mozbuild/test/backend/test_recursivemake.py b/python/mozbuild/mozbuild/test/backend/test_recursivemake.py
index 65f30acc756a..cd678869cf19 100644
--- a/python/mozbuild/mozbuild/test/backend/test_recursivemake.py
+++ b/python/mozbuild/mozbuild/test/backend/test_recursivemake.py
@@ -31,11 +31,9 @@ class TestRecursiveMakeBackend(BackendTester):
         expected = ['', 'dir1', 'dir2']
 
         for d in expected:
-            in_path = os.path.join(env.topsrcdir, d, 'Makefile.in')
             out_makefile = os.path.join(env.topobjdir, d, 'Makefile')
             out_backend = os.path.join(env.topobjdir, d, 'backend.mk')
 
-            self.assertTrue(os.path.exists(in_path))
             self.assertTrue(os.path.exists(out_makefile))
             self.assertTrue(os.path.exists(out_backend))
 
@@ -57,6 +55,18 @@ class TestRecursiveMakeBackend(BackendTester):
             'include $(topsrcdir)/config/rules.mk'
         ])
 
+    def test_missing_makefile_in(self):
+        """Ensure missing Makefile.in results in Makefile creation."""
+        env = self._consume('stub0', RecursiveMakeBackend)
+
+        p = os.path.join(env.topobjdir, 'dir2', 'Makefile')
+        self.assertTrue(os.path.exists(p))
+
+        lines = [l.strip() for l in open(p, 'rt').readlines()]
+        self.assertEqual(len(lines), 9)
+
+        self.assertTrue(lines[0].startswith('# THIS FILE WAS AUTOMATICALLY'))
+
     def test_backend_mk(self):
         """Ensure backend.mk file is written out properly."""
         env = self._consume('stub0', RecursiveMakeBackend)
@@ -67,6 +77,7 @@ class TestRecursiveMakeBackend(BackendTester):
         self.assertEqual(lines, [
             'MOZBUILD_DERIVED := 1',
             'NO_MAKEFILE_RULE := 1',
+            'NO_SUBMAKEFILES_RULE := 1',
             'DIRS := dir1',
             'PARALLEL_DIRS := dir2',
             'TEST_DIRS := dir3',
@@ -100,6 +111,7 @@ class TestRecursiveMakeBackend(BackendTester):
         self.assertEqual(lines, [
             'MOZBUILD_DERIVED := 1',
             'NO_MAKEFILE_RULE := 1',
+            'NO_SUBMAKEFILES_RULE := 1',
             'DIRS := dir',
             'PARALLEL_DIRS := p_dir',
             'DIRS += external',