diff --git a/src/ether_common.c b/src/ether_common.c
index 1e185ff..1a80e49 100644
--- a/src/ether_common.c
+++ b/src/ether_common.c
@@ -21,10 +21,17 @@
  * global variables exported to ether_*.c and possibly others
  */
 
+extern int     ether_fd;
+extern u_char  ether_host[6];
+extern const u_char  broadcast[6];
+extern int     ether_bsize;
+extern u_char *ether_buf;
+extern int     ETHEREventCount;
+
 int     ether_fd      = -1;    /* file descriptor for ether socket */
 
 u_char  ether_host[6] = {0, 0, 0, 0, 0, 0}; /* 48 bit address of this node */
-u_char  broadcast[6]  = {255, 255, 255, 255, 255, 255};
+const u_char  broadcast[6]  = {255, 255, 255, 255, 255, 255};
 
 int     ether_bsize   = 0;     /* if nonzero then a receive is pending */
 u_char *ether_buf     = NULL;  /* address of receive buffer */
diff --git a/src/ether_nethub.c b/src/ether_nethub.c
index a8bafb1..4f517ca 100644
--- a/src/ether_nethub.c
+++ b/src/ether_nethub.c
@@ -44,7 +44,7 @@
 
 extern int      ether_fd;      /* file descriptor for ether socket */
 extern u_char   ether_host[6]; /* 48 bit address of this node */
-extern u_char   broadcast[6];
+extern const u_char   broadcast[6];
 extern int      ether_bsize;   /* if nonzero then a receive is pending */
 extern u_char  *ether_buf;     /* address of receive buffer */
 extern LispPTR *PENDINGINTERRUPT68k;
diff --git a/src/ether_sunos.c b/src/ether_sunos.c
index 0b95a67..d64f0aa 100644
--- a/src/ether_sunos.c
+++ b/src/ether_sunos.c
@@ -83,7 +83,7 @@
 extern int      ether_fd;      /* file descriptor for ether socket */
 static int      ether_intf_type = 0;
 extern u_char   ether_host[6]; /* 48 bit address of this node */
-extern u_char   broadcast[6];
+extern const u_char   broadcast[6];
 extern int      ether_bsize;   /* if nonzero then a receive is pending */
 extern u_char  *ether_buf;     /* address of receive buffer */
 static u_char   nit_buf[3000]; /* the current chunk read from NIT (one packet) */