diff --git a/src/s/sunos4-1.h b/src/s/sunos4-1.h
index 241024249a8d40f1d1f8bbf02ec9e76e22ea88e8..7aa0946d3818583b711b8390f2b3e94ef25dfd89 100644
--- a/src/s/sunos4-1.h
+++ b/src/s/sunos4-1.h
@@ -39,3 +39,6 @@
 /* Tell GNU malloc to compensate for a bug in localtime.  */
 #define SUNOS_LOCALTIME_BUG
 #endif
+
+/* Define dlopen, dlclose, dlsym.  */
+#define USE_DL_STUBS