diff --git a/lodepng.cpp b/lodepng.cpp
index dfd5e4e..cf964d0 100644
--- a/lodepng.cpp
+++ b/lodepng.cpp
@@ -30,6 +30,8 @@ Rename this file to lodepng.cpp to use it for C++, or to lodepng.c to use it for
 
 #ifdef _MSC_VER
 #pragma warning (disable : 4201)
+
+#ifndef BASISU_NO_ITERATOR_DEBUG_LEVEL
 #if defined(_DEBUG) || defined(DEBUG)
 #define _ITERATOR_DEBUG_LEVEL 1
 #define _SECURE_SCL 1
@@ -38,6 +40,7 @@ Rename this file to lodepng.cpp to use it for C++, or to lodepng.c to use it for
 #define _ITERATOR_DEBUG_LEVEL 0
 #endif
 #endif
+#endif
 
 #include "lodepng.h"
 
diff --git a/transcoder/basisu.h b/transcoder/basisu.h
index 17d326a..339552f 100644
--- a/transcoder/basisu.h
+++ b/transcoder/basisu.h
@@ -19,6 +19,7 @@
 #pragma warning (disable : 4201)
 #pragma warning (disable : 4127) // warning C4127: conditional expression is constant
 #pragma warning (disable : 4530) // C++ exception handler used, but unwind semantics are not enabled.
+#ifndef BASISU_NO_ITERATOR_DEBUG_LEVEL
 //#define _HAS_ITERATOR_DEBUGGING 0
 #if defined(_DEBUG) || defined(DEBUG)
 #define _ITERATOR_DEBUG_LEVEL 1
@@ -27,6 +28,7 @@
 #define _SECURE_SCL 0
 #define _ITERATOR_DEBUG_LEVEL 0
 #endif
+#endif
 #ifndef NOMINMAX
 	#define NOMINMAX
 #endif