diff --git a/dom/bindings/GenerateCSS2PropertiesWebIDL.py b/dom/bindings/GenerateCSS2PropertiesWebIDL.py
index 57634494f..b1f2a6016 100644
--- a/dom/bindings/GenerateCSS2PropertiesWebIDL.py
+++ b/dom/bindings/GenerateCSS2PropertiesWebIDL.py
@@ -17,6 +17,7 @@ def generateLine(propName, extendedAttrs):
                                                  propName)
 def generate(output, idlFilename, preprocessorHeader):
     print(idlFilename)
+    sys.stdout.flush()
     cpp = list(buildconfig.substs['CPP'])
     cpp += shellutil.split(buildconfig.substs['ACDEFINES'])
     cpp.append(preprocessorHeader)
diff --git a/dom/bindings/mozwebidlcodegen/__init__.py b/dom/bindings/mozwebidlcodegen/__init__.py
index 69f3f5e25..93b33012a 100644
--- a/dom/bindings/mozwebidlcodegen/__init__.py
+++ b/dom/bindings/mozwebidlcodegen/__init__.py
@@ -12,6 +12,7 @@ import hashlib
 import json
 import logging
 import os
+import sys
 
 from copy import deepcopy
 
@@ -270,6 +271,7 @@ class WebIDLCodegenManager(LoggingMixin):
         for filename in sorted(changed_inputs):
             basename = mozpath.basename(filename)
             print basename
+            sys.stdout.flush()
             result.inputs.add(filename)
             written, deps = self._generate_build_files_for_webidl(filename)
             result.created |= written[0]