diff --git a/reactos/CMakeLists.txt b/reactos/CMakeLists.txt
index a507c306a41..385f94a3637 100644
--- a/reactos/CMakeLists.txt
+++ b/reactos/CMakeLists.txt
@@ -14,6 +14,9 @@ include(include/reactos/version.cmake)
 # Don't escape preprocessor definition values added via add_definitions
 cmake_policy(SET CMP0005 OLD)
 cmake_policy(SET CMP0002 NEW)
+if(POLICY CMP0018)
+    cmake_policy(SET CMP0018 OLD)
+endif()
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 set(CMAKE_INCLUDE_DIRECTORIES_PROJECT_BEFORE ON)
@@ -48,7 +51,7 @@ if(NOT CMAKE_CROSSCOMPILING)
 
     if(MSVC)
         if(ARCH MATCHES i386)
-            add_definitions(/DWIN32 /D_WINDOWS)
+            add_definitions(/D_X86_ /DWIN32 /D_WINDOWS)
         endif()
         add_definitions(/Dinline=__inline)
     else()
diff --git a/reactos/configure.cmd b/reactos/configure.cmd
index 514047b805b..713a0a581b2 100755
--- a/reactos/configure.cmd
+++ b/reactos/configure.cmd
@@ -16,6 +16,8 @@ if defined ROS_ARCH (
         set CMAKE_GENERATOR="CodeBlocks - MinGW Makefiles"
     ) else if /I "%1" == "Eclipse" (
         set CMAKE_GENERATOR="Eclipse CDT4 - MinGW Makefiles"
+    ) else if /I "%1" == "Ninja" (
+        set CMAKE_GENERATOR="Ninja"
     ) else (
         set CMAKE_GENERATOR="MinGW Makefiles"
     )
@@ -106,6 +108,8 @@ if %USE_NMAKE% == 1 (
         set CMAKE_GENERATOR="Eclipse CDT4 - NMake Makefiles"
     ) else if /I "%1" == "JOM" (
         set CMAKE_GENERATOR="NMake Makefiles JOM"
+    ) else if /I "%1" == "Ninja" (
+        set CMAKE_GENERATOR="Ninja"
     ) else (
         set CMAKE_GENERATOR="NMake Makefiles"
     )