diff --git a/reactos/include/wingdi.h b/reactos/include/wingdi.h
index cab8daaa470..60a3dc06d3f 100644
--- a/reactos/include/wingdi.h
+++ b/reactos/include/wingdi.h
@@ -1128,6 +1128,7 @@ extern "C" {
 #define TT_POLYGON_TYPE 24
 #define TT_PRIM_LINE 1
 #define TT_PRIM_QSPLINE 2
+#define TT_PRIM_CSPLINE 3
 #define FONTMAPPER_MAX 10
 #define ENHMETA_STOCK_OBJECT 0x80000000
 #define WGL_FONT_LINES 0