diff --git a/cmake/externals/bullet/CMakeLists.txt b/cmake/externals/bullet/CMakeLists.txt
index 4fb8b0a5d1..3c83b84fcd 100644
--- a/cmake/externals/bullet/CMakeLists.txt
+++ b/cmake/externals/bullet/CMakeLists.txt
@@ -52,16 +52,16 @@ endif ()
 
 if (DEFINED BULLET_LIB_EXT)
   set(${EXTERNAL_NAME_UPPER}_DYNAMICS_LIBRARY_RELEASE ${BULLET_LIB_DIR}/${LIB_PREFIX}BulletDynamics.${BULLET_LIB_EXT} CACHE FILEPATH "Bullet dynamics release library location")
-  set(${EXTERNAL_NAME_UPPER}_DYNAMICS_LIBRARY_DEBUG NOTFOUND CACHE FILEPATH "Bullet dynamics debug library location")
+  set(${EXTERNAL_NAME_UPPER}_DYNAMICS_LIBRARY_DEBUG "" CACHE FILEPATH "Bullet dynamics debug library location")
 
   set(${EXTERNAL_NAME_UPPER}_COLLISION_LIBRARY_RELEASE ${BULLET_LIB_DIR}/${LIB_PREFIX}BulletCollision.${BULLET_LIB_EXT} CACHE FILEPATH "Bullet collision release library location")
-  set(${EXTERNAL_NAME_UPPER}_COLLISION_LIBRARY_DEBUG NOTFOUND CACHE FILEPATH "Bullet collision debug library location")
+  set(${EXTERNAL_NAME_UPPER}_COLLISION_LIBRARY_DEBUG "" CACHE FILEPATH "Bullet collision debug library location")
 
   set(${EXTERNAL_NAME_UPPER}_MATH_LIBRARY_RELEASE ${BULLET_LIB_DIR}/${LIB_PREFIX}LinearMath.${BULLET_LIB_EXT} CACHE FILEPATH "Bullet math release library location")
-  set(${EXTERNAL_NAME_UPPER}_MATH_LIBRARY_DEBUG NOTFOUND CACHE FILEPATH "Bullet math debug library location")
+  set(${EXTERNAL_NAME_UPPER}_MATH_LIBRARY_DEBUG "" CACHE FILEPATH "Bullet math debug library location")
 
   set(${EXTERNAL_NAME_UPPER}_SOFTBODY_LIBRARY_RELEASE ${BULLET_LIB_DIR}/${LIB_PREFIX}BulletSoftBody.${BULLET_LIB_EXT} CACHE FILEPATH "Bullet softbody release library location")
-  set(${EXTERNAL_NAME_UPPER}_SOFTBODY_LIBRARY_DEBUG NOTFOUND CACHE FILEPATH "Bullet softbody debug library location")
+  set(${EXTERNAL_NAME_UPPER}_SOFTBODY_LIBRARY_DEBUG "" CACHE FILEPATH "Bullet softbody debug library location")
 endif ()
 
 if (DEFINED ${EXTERNAL_NAME_UPPER}_DYNAMICS_LIBRARY_RELEASE)
diff --git a/cmake/externals/glew/CMakeLists.txt b/cmake/externals/glew/CMakeLists.txt
index e960eb8bcb..0d80e7a789 100644
--- a/cmake/externals/glew/CMakeLists.txt
+++ b/cmake/externals/glew/CMakeLists.txt
@@ -20,7 +20,7 @@ if (WIN32)
   set(_LIB_DIR ${SOURCE_DIR}/lib/Release/Win32)
   
   set(${EXTERNAL_NAME_UPPER}_LIBRARY_RELEASE ${_LIB_DIR}/glew32.lib CACHE FILEPATH "Location of GLEW release library")
-  set(${EXTERNAL_NAME_UPPER}_LIBRARY_DEBUG NOTFOUND CACHE FILEPATH "Location of GLEW debug library")
+  set(${EXTERNAL_NAME_UPPER}_LIBRARY_DEBUG "" CACHE FILEPATH "Location of GLEW debug library")
   
   set(${EXTERNAL_NAME_UPPER}_DLL_PATH ${SOURCE_DIR}/bin/Release/Win32 CACHE FILEPATH "Location of GLEW DLL")
 endif ()
\ No newline at end of file