diff --git a/src/afs/SOLARIS/osi_groups.c b/src/afs/SOLARIS/osi_groups.c
index 7e0456ff91..d6e7a993fe 100644
--- a/src/afs/SOLARIS/osi_groups.c
+++ b/src/afs/SOLARIS/osi_groups.c
@@ -36,11 +36,14 @@ static int
 		int change_parent);
 
 
+#ifdef AFS_SUN511_ENV
+int64_t
+#else
 int
-afs_xsetgroups(uap, rvp)
-     u_int uap;			/* this is gidsetsize */
-     gid_t *rvp;		/* this is gidset */
+#endif
+afs_xsetgroups(u_int uap, gid_t *rvp)
 {
+    /* 'uap' is our gidsetsize; 'rvp' is our gidset */
     int code = 0;
     struct vrequest treq;
     struct proc *proc = ttoproc(curthread);
diff --git a/src/afs/SOLARIS/osi_prototypes.h b/src/afs/SOLARIS/osi_prototypes.h
index 7fd6e6107c..02baea7cf3 100644
--- a/src/afs/SOLARIS/osi_prototypes.h
+++ b/src/afs/SOLARIS/osi_prototypes.h
@@ -23,4 +23,12 @@ int afs_putpage(struct vnode *vp, offset_t off, u_int len, int flags,
 int afs_putapage(struct vnode *vp, struct page *pages, u_offset_t * offp,
 		 size_t * lenp, int flags, afs_ucred_t *credp);
 
+/* osi_groups.c */
+
+#ifdef AFS_SUN511_ENV
+int64_t afs_xsetgroups(u_int uap, gid_t *rvp);
+#else
+int afs_xsetgroups(u_int uap, gid_t *rvp);
+#endif
+
 #endif /* _OSI_PROTOTYPES_H_ */
diff --git a/src/afs/SOLARIS/osi_vfsops.c b/src/afs/SOLARIS/osi_vfsops.c
index 54751519e1..7472179952 100644
--- a/src/afs/SOLARIS/osi_vfsops.c
+++ b/src/afs/SOLARIS/osi_vfsops.c
@@ -394,8 +394,6 @@ afsinit(int fstype, char *dummy)
 afsinit(struct vfssw *vfsswp, int fstype)
 #endif
 {
-    extern int afs_xsetgroups();
-
     AFS_STATCNT(afsinit);
 
     afs_orig_setgroups = sysent[SYS_setgroups].sy_callc;