diff --git a/include/winbase.h b/include/winbase.h
index 2f6c2f4..56177f0 100644
--- a/include/winbase.h
+++ b/include/winbase.h
@@ -589,6 +589,7 @@
 #define CREATE_UNICODE_ENVIRONMENT  0x00000400
 #define CREATE_SEPARATE_WOW_VDM     0x00000800
 #define CREATE_SHARED_WOW_VDM       0x00001000
+#define STACK_SIZE_PARAM_IS_A_RESERVATION 0x00010000
 #define CREATE_DEFAULT_ERROR_MODE   0x04000000
 #define CREATE_NO_WINDOW            0x08000000
 #define PROFILE_USER                0x10000000