diff --git a/lib/config-dos.h b/lib/config-dos.h
index 863539b737bdce827543f40fcc7d540bf333ca09..bb0315e2cbdd46994d41227bedd9b9e1879b52d2 100644
--- a/lib/config-dos.h
+++ b/lib/config-dos.h
@@ -67,6 +67,7 @@
 #define SIZEOF_INT             4
 #define SIZEOF_LONG_DOUBLE     16
 #define SIZEOF_SHORT           2
+#define SIZEOF_SIZE_T          4
 #define STDC_HEADERS           1
 #define TIME_WITH_SYS_TIME     1