diff --git a/core/rosbuild/rosbuild.cmake b/core/rosbuild/rosbuild.cmake
index 82afe9bf..5bb41153 100644
--- a/core/rosbuild/rosbuild.cmake
+++ b/core/rosbuild/rosbuild.cmake
@@ -15,6 +15,8 @@ if(COMMAND cmake_policy)
   endif(POLICY CMP0011)
 endif(COMMAND cmake_policy)
 
+set(CMAKE_OSX_ARCHITECTURES "x86_64")
+
 ##############################################################################
 # First things first: we must have rospack.
 find_program(ROSPACK_EXE NAMES rospack DOC "rospack executable")
diff --git a/tools/rospack/CMakeLists.txt b/tools/rospack/CMakeLists.txt
index 1df1b704..7da9be77 100644
--- a/tools/rospack/CMakeLists.txt
+++ b/tools/rospack/CMakeLists.txt
@@ -7,6 +7,8 @@ endif()
 cmake_minimum_required(VERSION 2.4.6)
 set(CMAKE_BUILD_TYPE Release)
 
+set(CMAKE_OSX_ARCHITECTURES "x86_64")
+
 set(CMAKE_INSTALL_PREFIX /tmp/rospack)
 #set(CMAKE_INSTALL_RPATH_USE_LINK_RPATH true)
 #set(CMAKE_SKIP_BUILD_RPATH true)