diff --git a/CMakeLists.txt b/CMakeLists.txt
index fb1e94caa66..a020f416ce5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -47,7 +47,9 @@ if (${CMAKE_SYSTEM} MATCHES "Darwin")
 endif()
 
 if (WIN32)
-    set(ICONV_DIR "${CMAKE_SOURCE_DIR}/winbuild")
+    if(NOT ICONV_DIR)
+      set(ICONV_DIR "${CMAKE_SOURCE_DIR}/winbuild")
+    endif()
     set(CMAKE_REQUIRED_DEFINITIONS "-DLIBICONV_STATIC")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /bigobj") # needed for language.cpp on 64bit
     add_definitions(-DLIBICONV_STATIC -D_CRT_SECURE_NO_WARNINGS)