diff --git a/reactos/include/pe.h b/reactos/include/pe.h
index 8f13173f6cd..e5a3e9105b2 100644
--- a/reactos/include/pe.h
+++ b/reactos/include/pe.h
@@ -130,6 +130,15 @@ typedef struct _IMAGE_OPTIONAL_HEADER {
     IMAGE_DATA_DIRECTORY DataDirectory[IMAGE_NUMBEROF_DIRECTORY_ENTRIES];
 } IMAGE_OPTIONAL_HEADER, *PIMAGE_OPTIONAL_HEADER;
 
+#define IMAGE_SUBSYSTEM_UNKNOWN		0
+#define IMAGE_SUBSYSTEM_NATIVE		1
+#define IMAGE_SUBSYSTEM_WINDOWS_GUI	2
+#define IMAGE_SUBSYSTEM_WINDOWS_CUI	3
+#define IMAGE_SUBSYSTEM_OS2_GUI		4
+#define IMAGE_SUBSYSTEM_OS2_CUI		5
+#define IMAGE_SUBSYSTEM_POSIX_GUI	6
+#define IMAGE_SUBSYSTEM_POSIX_CUI	7
+#define IMAGE_SUBSYSTEM_WINDOWS_CE_GUI	9
 
 typedef struct _IMAGE_NT_HEADERS {
     DWORD Signature;