diff --git a/reactos/include/crt/float.h b/reactos/include/crt/float.h
index a542686948c..d80ae0ec295 100644
--- a/reactos/include/crt/float.h
+++ b/reactos/include/crt/float.h
@@ -41,6 +41,7 @@
 #define	_MCW_IC		0x00040000	/* Infinity */
 #define	_MCW_RC		0x00000300	/* Rounding */
 #define	_MCW_PC		0x00030000	/* Precision */
+#define _MCW_DN     0x03000000  /* Denormal */
 
 /* Control word values for unNew (use with related unMask above) */
 #define	_EM_INVALID	0x00000010