diff --git a/collada_urdf/CMakeLists.txt b/collada_urdf/CMakeLists.txt
index bca56e9..fc93e4c 100644
--- a/collada_urdf/CMakeLists.txt
+++ b/collada_urdf/CMakeLists.txt
@@ -24,10 +24,10 @@ if ( NOT ASSIMP_FOUND )
   endif()
 endif()
 if( ASSIMP_FOUND )
-  if( NOT ${ASSIMP_VERSION} STRLESS "2.0.1150" )
+  if( NOT ${ASSIMP_VERSION} VERSION_LESS "2.0.1150" )
     add_definitions(-DASSIMP_UNIFIED_HEADER_NAMES)
   endif()
-  if( NOT ${ASSIMP_VERSION} STRLESS "2.0.885" )
+  if( NOT ${ASSIMP_VERSION} VERSION_LESS "2.0.885" )
     add_definitions(-DASSIMP_EXPORT_API)
   endif()
   include_directories(${ASSIMP_INCLUDE_DIRS})