diff --git a/CMakeLists.txt b/CMakeLists.txt
index ab546a9f..3b507b44 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -104,6 +104,12 @@ if (WITHOUT_CLIENT)
 	set(LWS_NO_CLIENT 1)
 endif()
 
+if (WITHOUT_DEBUG)
+	set(_DEBUG 0)
+else()
+	set(_DEBUG 1)
+endif()
+
 if (MINGW)
 	set(LWS_MINGW_SUPPORT 1)
 endif()
diff --git a/config.h.cmake b/config.h.cmake
index 92882672..e55d7154 100644
--- a/config.h.cmake
+++ b/config.h.cmake
@@ -1,5 +1,9 @@
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
+#ifndef WIN32
+#cmakedefine _DEBUG
+#endif
+
 /* Define to 1 to use CyaSSL as a replacement for OpenSSL. 
  * LWS_OPENSSL_SUPPORT needs to be set also for this to work. */
 #cmakedefine USE_CYASSL