diff --git a/os2/owos2.mak b/os2/owos2.mak
index f80f8687..13784537 100644
--- a/os2/owos2.mak
+++ b/os2/owos2.mak
@@ -42,7 +42,7 @@ CFLAGS  = /oneatx
 LDFLAGS =
 !endif
 
-CPPFLAGS = /i=$(PDCURSES_HOME)
+CPPFLAGS = /i=$(PDCURSES_HOME) /i=$(CCINCDIR)
 
 CCFLAGS = /bt=$(TARGET) /bm /3s /wx /s /zq /mf $(CFLAGS) $(CPPFLAGS)