--- CMakeLists.txt
+++ CMakeLists.txt
@@ -79,10 +79,10 @@
 SET(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake) # for FindReadline.cmake
 
 # external packages
-FIND_PACKAGE( BZip2 )
-FIND_PACKAGE( ZLIB )
-FIND_PACKAGE( Readline )
-FIND_PACKAGE( Editline )
+FIND_PACKAGE( BZip2    NO_SYSTEM_ENVIRONMENT_PATH )
+FIND_PACKAGE( ZLIB     NO_SYSTEM_ENVIRONMENT_PATH )
+FIND_PACKAGE( Readline NO_SYSTEM_ENVIRONMENT_PATH )
+FIND_PACKAGE( Editline NO_SYSTEM_ENVIRONMENT_PATH )
 
 # Configuration checks
 
