diff --git a/crypto/dso/dso_dlfcn.c b/crypto/dso/dso_dlfcn.c
index 7da3f78928..14bd322fb8 100644
--- a/crypto/dso/dso_dlfcn.c
+++ b/crypto/dso/dso_dlfcn.c
@@ -78,6 +78,9 @@ DSO_METHOD *DSO_METHOD_dlfcn(void)
 #else
 
 #ifdef HAVE_DLFCN_H
+# ifdef __osf__
+#  define __EXTENSIONS__
+# endif
 # include <dlfcn.h>
 # define HAVE_DLINFO 1
 # if defined(_AIX) || defined(__CYGWIN__) || \