diff --git a/SheepShaver/src/Unix/prefs_editor_gtk.cpp b/SheepShaver/src/Unix/prefs_editor_gtk.cpp
index aa5962c8..0641d556 100644
--- a/SheepShaver/src/Unix/prefs_editor_gtk.cpp
+++ b/SheepShaver/src/Unix/prefs_editor_gtk.cpp
@@ -815,7 +815,17 @@ static GList *add_serial_names(void)
 	if (d) {
 		struct dirent *de;
 		while ((de = readdir(d)) != NULL) {
+#if defined(__linux__)
 			if (strncmp(de->d_name, "ttyS", 4) == 0 || strncmp(de->d_name, "lp", 2) == 0) {
+#elif defined(__FreeBSD__)
+			if (strncmp(de->d_name, "cuaa", 4) == 0 || strncmp(de->d_name, "lpt", 3) == 0) {
+#elif defined(__NetBSD__)
+			if (strncmp(de->d_name, "tty0", 4) == 0 || strncmp(de->d_name, "lpt", 3) == 0) {
+#elif defined(sgi)
+			if (strncmp(de->d_name, "ttyf", 4) == 0 || strncmp(de->d_name, "plp", 3) == 0) {
+#else
+			if (false) {
+#endif
 				char *str = new char[64];
 				sprintf(str, "/dev/%s", de->d_name);
 				glist = g_list_append(glist, str);
@@ -846,7 +856,13 @@ static GList *add_ether_names(void)
 			struct ifreq req, *ifr = ifc.ifc_req;
 			for (int i=0; i<ifc.ifc_len; i+=sizeof(ifreq), ifr++) {
 				req = *ifr;
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(sgi)
+				if (ioctl(s, SIOCGIFADDR, &req) == 0 && (req.ifr_addr.sa_family == ARPHRD_ETHER || req.ifr_addr.sa_family == ARPHRD_ETHER+1)) {
+#elif defined(__linux__)
 				if (ioctl(s, SIOCGIFHWADDR, &req) == 0 && req.ifr_hwaddr.sa_family == ARPHRD_ETHER) {
+#else
+				if (false) {
+#endif
 					char *str = new char[64];
 					strncpy(str, ifr->ifr_name, 63);
 					glist = g_list_append(glist, str);
diff --git a/SheepShaver/src/Unix/sysdeps.h b/SheepShaver/src/Unix/sysdeps.h
index 9d52661e..517cb234 100644
--- a/SheepShaver/src/Unix/sysdeps.h
+++ b/SheepShaver/src/Unix/sysdeps.h
@@ -44,6 +44,10 @@
 #include <string.h>
 #include <signal.h>
 
+#ifdef HAVE_PTHREADS
+# include <pthread.h>
+#endif
+
 #ifdef HAVE_FCNTL_H
 # include <fcntl.h>
 #endif
@@ -356,8 +360,10 @@ typedef struct timeval tm_time_t;
 extern uint64 GetTicks_usec(void);
 extern void Delay_usec(uint32 usec);
 
+#ifdef HAVE_PTHREADS
 // Setup pthread attributes
 extern void Set_pthread_attr(pthread_attr_t *attr, int priority);
+#endif
 
 // Various definitions
 typedef struct rgb_color {