diff --git a/CHANGES b/CHANGES
index 813feff..d059101 100644
--- a/CHANGES
+++ b/CHANGES
@@ -12,6 +12,8 @@ Features:
 Coding:
 	Introduced groups_t instead of uint32_t, for more flexibility
 
+	Rearranged option group bits to only require 32 bits on older systems.
+
 ####################### V 1.7.4.5 (not released):
 
 Corrections:
diff --git a/xio-socket.c b/xio-socket.c
index 6aa0a5e..78ff176 100644
--- a/xio-socket.c
+++ b/xio-socket.c
@@ -51,7 +51,7 @@ int xioopen_socket_recvfrom(int argc, const char *argv[], struct opt *opts,
 			    int dummy1, int socktype, int dummy3);
 static
 int xioopen_socket_recv(int argc, const char *argv[], struct opt *opts,
-			int xioflags, xiofile_t *xfd, groups_t groups, 
+			int xioflags, xiofile_t *xfd, groups_t groups,
 			int dummy1, int dummy2, int dummy3);
 
 static
diff --git a/xio-unix.c b/xio-unix.c
index 4c36de4..6315a66 100644
--- a/xio-unix.c
+++ b/xio-unix.c
@@ -586,7 +586,7 @@ static int xioopen_unix_client(int argc, const char *argv[], struct opt *opts, i
    OPT_PROTOCOL_FAMILY, OPT_UNIX_TIGHTSOCKLEN, OPT_UNLINK_CLOSE, OPT_BIND,
    OPT_SO_TYPE, OPT_SO_PROTOTYPE, OPT_CLOEXEC, OPT_USER, OPT_GROUP, ?OPT_FORK,
 */
-int 
+int
 _xioopen_unix_client(xiosingle_t *xfd, int xioflags, groups_t groups,
 		     int abstract, struct opt *opts, const char *name) {
    const struct opt *namedopt;
diff --git a/xio.h b/xio.h
index 63e8b7d..e10daf3 100644
--- a/xio.h
+++ b/xio.h
@@ -89,8 +89,14 @@ enum xiotag {
 			   streams */
 } ;
 
+/* Keep condition consistent with xioopts.h:GROUP_*! */
+#if WITH_SCTP
+typedef uint64_t groups_t;
+#define F_groups_t F_uint64_x
+#else
 typedef uint32_t groups_t;
 #define F_groups_t F_uint32_x
+#endif
 
 /* global XIO options/parameters */
 typedef struct {
diff --git a/xiohelp.c b/xiohelp.c
index 26f3343..71256de 100644
--- a/xiohelp.c
+++ b/xiohelp.c
@@ -48,10 +48,10 @@ static const char *addressgroupnames[] = {
 	"TERMIOS",	"RANGE",	"PTY",		"PARENT",
 	"UNIX",		"IP4",		"IP6",		"INTERFACE",
 	"UDP",		"TCP",		"SOCKS4",	"OPENSSL",
-	"PROCESS",	"APPL",		"HTTP",		"SCTP"
+	"PROCESS",	"APPL",		"HTTP",		"undef",
+	"SCTP"
 } ;
 
-
 /* keep consistent with xioopts.h:enum ephase ! */
 static char *optionphasenames[] = {
 	"ALL",		"INIT",		"EARLY",
diff --git a/xioopts.c b/xioopts.c
index 1731cd5..485fa46 100644
--- a/xioopts.c
+++ b/xioopts.c
@@ -2780,7 +2780,7 @@ groups_t _groupbits(mode_t mode) {
       result = GROUP_SOCKET|GROUP_SOCK_UNIX; break;
 #endif
    }
-   Debug2("_groupbits(%d) -> %d", mode, result);
+   Debug2("_groupbits("F_mode") -> "F_groups_t, mode, result);
    return result;
 }
 
diff --git a/xioopts.h b/xioopts.h
index ac36e95..2e2f808 100644
--- a/xioopts.h
+++ b/xioopts.h
@@ -176,10 +176,19 @@ enum e_func {
 #define GROUP_PROCESS	0x10000000	/* a process related option */
 #define GROUP_APPL	0x20000000	/* option handled by data loop */
 #define GROUP_HTTP	0x40000000	/* any HTTP client */
-#define GROUP_IP_SCTP	0x80000000U
 
-#define GROUP_ANY	(GROUP_PROCESS|GROUP_APPL)
+/* Keep condition consistent with xio.h:groups_t! */
+#if WITH_SCTP
+/* The following groups are not expected on systems without uint64_t */
+#define GROUP_IP_SCTP	0x0100000000U
+#define GROUP_ALL	0x03ffffffffU
+#else
+#define GROUP_IP_SCTP	0
 #define GROUP_ALL	0xffffffffU
+#endif
+
+#define GROUP_IPAPP	(GROUP_IP_UDP|GROUP_IP_TCP|GROUP_IP_SCTP)	/* true: indicates one of UDP, TCP, SCTP */
+#define GROUP_ANY	(GROUP_PROCESS|GROUP_APPL)
 
 
 /* no IP multicasts, no error queue yet */