diff --git a/CMakeLists.txt b/CMakeLists.txt
index 18cc6f23..a1fb47e8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,7 +11,7 @@ if(MSVC)
         "/EHsc"
     )
 
-    STRING(REPLACE "-O2" "-Od" CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE})
+    STRING(REPLACE "/O2" "/Od" CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE})
 
     add_definitions(-D_SCL_SECURE_NO_WARNINGS)
 else(MSVC)