diff --git a/src/blacksound/dsp/SimpleHeader.h b/src/blacksound/dsp/SimpleHeader.h
index 2e54e998d..df346be7a 100644
--- a/src/blacksound/dsp/SimpleHeader.h
+++ b/src/blacksound/dsp/SimpleHeader.h
@@ -26,16 +26,17 @@
  *	DEALINGS IN THE SOFTWARE.
  */
 
+#ifndef BLACKSOUND_DSP_SIMPLE_HEADER_H
+#define BLACKSOUND_DSP_SIMPLE_HEADER_H
 
-#ifndef __SIMPLE_HEADER_H__
-#define __SIMPLE_HEADER_H__
-
-#if _MSC_VER > 1000			// MS Visual Studio
-#define INLINE __forceinline	// forces inline
-#define NOMINMAX				// for standard library min(), max()
-#define _USE_MATH_DEFINES		// for math constants
-#else						// other IDE's
-#define INLINE inline
+#if _MSC_VER > 1000 // MS Visual Studio
+#   define INLINE __forceinline  // forces inline
+#   define NOMINMAX              // for standard library min(), max()
+#   ifndef M_PI
+#       define _USE_MATH_DEFINES // for math constants
+#   endif
+#else  // other IDE's
+#   define INLINE inline
 #endif
 
 #include <algorithm>	// for min(), max()