diff --git a/CMakeLists.txt b/CMakeLists.txt
index faa234f90..a435fecb5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -200,7 +200,7 @@ endif()
 if(USE_SHARED_ZLIB)
   find_package(ZLIB REQUIRED)
 else()
-  set(ZLIB_FOUND)
+  set(ZLIB_FOUND ON)
   set(ZLIB_LIBRARY zlibstatic)
   set(ZLIB_LIBRARIES ${ZLIB_LIBRARY})
   set(ZLIB_INCLUDE_DIRS