diff --git a/CMakeLists.txt b/CMakeLists.txt
index af9d1a72..f33bd8b0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -40,7 +40,7 @@ MESSAGE(STATUS "Detecting readline support")
 if (READLINE_LIBRARY)
     MESSAGE(STATUS "Found: ${READLINE_LIBRARY}")
     SET (READLINE_LIB readline)
-    SET (READLINE_FLAG " -DREADLINE_AVAILABLE")
+    ADD_DEFINITIONS(/DREADLINE_AVAILABLE)
 else(READLINE_LIBRARY)
     MESSAGE(STATUS "Not Found")
     SET (READLINE_LIB )