diff --git a/accessible/windows/ia2/Makefile.in b/accessible/windows/ia2/Makefile.in
deleted file mode 100644
index 23e125e87c2..00000000000
--- a/accessible/windows/ia2/Makefile.in
+++ /dev/null
@@ -1,9 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-# The midl generated code include Windows headers which defines min and max
-# macros which conflicts with std::min/max.  Suppress the macros:
-OS_CXXFLAGS += -DNOMINMAX
-
-include $(topsrcdir)/config/rules.mk
diff --git a/accessible/windows/ia2/moz.build b/accessible/windows/ia2/moz.build
index 8d207ed47e2..2c0ef388c33 100644
--- a/accessible/windows/ia2/moz.build
+++ b/accessible/windows/ia2/moz.build
@@ -45,3 +45,8 @@ LOCAL_INCLUDES += [
 ]
 
 FINAL_LIBRARY = 'xul'
+
+# The midl generated code include Windows headers which defines min and max
+# macros which conflicts with std::min/max.  Suppress the macros:
+if CONFIG['OS_ARCH'] == 'WINNT':
+    DEFINES['NOMINMAX'] = True
diff --git a/accessible/windows/uia/Makefile.in b/accessible/windows/uia/Makefile.in
deleted file mode 100644
index 23e125e87c2..00000000000
--- a/accessible/windows/uia/Makefile.in
+++ /dev/null
@@ -1,9 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-# The midl generated code include Windows headers which defines min and max
-# macros which conflicts with std::min/max.  Suppress the macros:
-OS_CXXFLAGS += -DNOMINMAX
-
-include $(topsrcdir)/config/rules.mk
diff --git a/accessible/windows/uia/moz.build b/accessible/windows/uia/moz.build
index 3431d126ed5..6f98f6882a6 100644
--- a/accessible/windows/uia/moz.build
+++ b/accessible/windows/uia/moz.build
@@ -18,3 +18,8 @@ LOCAL_INCLUDES += [
 ]
 
 FINAL_LIBRARY = 'xul'
+
+# The midl generated code include Windows headers which defines min and max
+# macros which conflicts with std::min/max.  Suppress the macros:
+if CONFIG['OS_ARCH'] == 'WINNT':
+    DEFINES['NOMINMAX'] = True
diff --git a/content/media/directshow/Makefile.in b/content/media/directshow/Makefile.in
deleted file mode 100644
index 64225645225..00000000000
--- a/content/media/directshow/Makefile.in
+++ /dev/null
@@ -1,7 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-ifeq ($(OS_ARCH),WINNT)
-OS_CXXFLAGS += -DNOMINMAX
-endif
diff --git a/content/media/directshow/moz.build b/content/media/directshow/moz.build
index 5c2e0008e6a..a939640417e 100644
--- a/content/media/directshow/moz.build
+++ b/content/media/directshow/moz.build
@@ -42,3 +42,5 @@ LOCAL_INCLUDES += [
     '/media/webrtc/trunk/webrtc/modules/video_capture/windows',
 ]
 
+if CONFIG['OS_ARCH'] == 'WINNT':
+    DEFINES['NOMINMAX'] = True
diff --git a/content/media/fmp4/Makefile.in b/content/media/fmp4/Makefile.in
deleted file mode 100644
index 64225645225..00000000000
--- a/content/media/fmp4/Makefile.in
+++ /dev/null
@@ -1,7 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-ifeq ($(OS_ARCH),WINNT)
-OS_CXXFLAGS += -DNOMINMAX
-endif
diff --git a/content/media/fmp4/moz.build b/content/media/fmp4/moz.build
index bc6ef9a3120..a01735fe79c 100644
--- a/content/media/fmp4/moz.build
+++ b/content/media/fmp4/moz.build
@@ -61,3 +61,6 @@ if CONFIG['MOZ_APPLEMEDIA']:
 FINAL_LIBRARY = 'xul'
 
 FAIL_ON_WARNINGS = True
+
+if CONFIG['OS_ARCH'] == 'WINNT':
+    DEFINES['NOMINMAX'] = True
diff --git a/content/media/wmf/Makefile.in b/content/media/wmf/Makefile.in
deleted file mode 100644
index 64225645225..00000000000
--- a/content/media/wmf/Makefile.in
+++ /dev/null
@@ -1,7 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-ifeq ($(OS_ARCH),WINNT)
-OS_CXXFLAGS += -DNOMINMAX
-endif
diff --git a/content/media/wmf/moz.build b/content/media/wmf/moz.build
index 20c033f515a..6b1d653ee9a 100644
--- a/content/media/wmf/moz.build
+++ b/content/media/wmf/moz.build
@@ -27,3 +27,6 @@ SOURCES += [
 FAIL_ON_WARNINGS = True
 
 FINAL_LIBRARY = 'xul'
+
+if CONFIG['OS_ARCH'] == 'WINNT':
+    DEFINES['NOMINMAX'] = True