diff --git a/CMakeLists.txt b/CMakeLists.txt
index 770fa046..e537aeb3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -101,8 +101,21 @@ math(EXPR TAGLIB_SOVERSION_PATCH "${TAGLIB_SOVERSION_REVISION}")
 
 include(ConfigureChecks.cmake)
 
-if(${ZLIB_FOUND})
-  set(ZLIB_LIBRARIES_FLAGS -lz)
+# Determine whether zlib is installed.
+
+if(NOT ZLIB_SOURCE)
+  find_package(ZLIB)
+  if(ZLIB_FOUND)
+    set(HAVE_ZLIB 1)
+    set(ZLIB_LIBRARIES_FLAGS -lz)
+  else()
+    set(HAVE_ZLIB 0)
+  endif()
+endif()
+
+if(NOT HAVE_ZLIB AND ZLIB_SOURCE)
+  set(HAVE_ZLIB 1)
+  set(HAVE_ZLIB_SOURCE 1)
 endif()
 
 if(NOT WIN32)
@@ -120,11 +133,6 @@ if(NOT BUILD_FRAMEWORK)
   install(FILES "${CMAKE_CURRENT_BINARY_DIR}/taglib.pc" DESTINATION "${LIB_INSTALL_DIR}/pkgconfig")
 endif()
 
-if(NOT HAVE_ZLIB AND ZLIB_SOURCE)
-  set(HAVE_ZLIB 1)
-  set(HAVE_ZLIB_SOURCE 1)
-endif()
-
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 configure_file(config.h.cmake "${CMAKE_CURRENT_BINARY_DIR}/config.h")
 
diff --git a/ConfigureChecks.cmake b/ConfigureChecks.cmake
index 2fe2f129..7d2ff953 100644
--- a/ConfigureChecks.cmake
+++ b/ConfigureChecks.cmake
@@ -176,17 +176,6 @@ check_cxx_source_compiles("
   }
 " HAVE_ISO_STRDUP)
 
-# Determine whether zlib is installed.
-
-if(NOT ZLIB_SOURCE)
-  find_package(ZLIB)
-  if(ZLIB_FOUND)
-    set(HAVE_ZLIB 1)
-  else()
-    set(HAVE_ZLIB 0)
-  endif()
-endif()
-
 # Detect WinRT mode
 if(CMAKE_SYSTEM_NAME STREQUAL "WindowsStore")
 	set(PLATFORM WINRT 1)