diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2d35835..0be112e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,7 +52,7 @@
   find_package(ZLIB)
 
   if(ZLIB_FOUND)
-    include_directories(ZLIB_INCLUDE_DIR)
+    include_directories(${ZLIB_INCLUDE_DIR})
   endif(ZLIB_FOUND)
 endif(ENABLE_ZLIB_SUPPORT)