diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8951532d5..6c1910385 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -183,7 +183,7 @@ OPTION(ASSIMP_BUILD_ZLIB
 
 IF ( NOT ASSIMP_BUILD_ZLIB )
     find_package(ZLIB)
-ENDIF(ASSIMP_BUILD_ZLIB)
+ENDIF( NOT ASSIMP_BUILD_ZLIB )
 
 IF( NOT ZLIB_FOUND )
   message(STATUS "compiling zlib from souces")