diff --git a/sys/net/slcompress.h b/sys/net/slcompress.h
index 4e20c3768c40..6959db0671bb 100644
--- a/sys/net/slcompress.h
+++ b/sys/net/slcompress.h
@@ -119,8 +119,13 @@ struct cstate {
 	u_int16_t cs_hlen;	/* size of hdr (receive only) */
 	u_char cs_id;		/* connection # associated with this state */
 	u_char cs_filler;
-	struct ip cs_ip;	/* ip/tcp hdr from most recent packet */
+	union {
+		char csu_hdr[MAX_HDR];
+		struct ip csu_ip;	/* ip/tcp hdr from most recent packet */
+	} slcs_u;
 };
+#define cs_ip slcs_u.csu_ip
+#define cs_hdr slcs_u.csu_hdr
 
 /*
  * all the state data for one serial line (we need one of these
diff --git a/usr.sbin/ppp/slcompress.h b/usr.sbin/ppp/slcompress.h
index 85aee7432f95..099771be134f 100644
--- a/usr.sbin/ppp/slcompress.h
+++ b/usr.sbin/ppp/slcompress.h
@@ -102,8 +102,14 @@ struct cstate {
   u_short cs_hlen;		/* size of hdr (receive only) */
   u_char cs_id;			/* connection # associated with this state */
   u_char cs_filler;
-  struct ip cs_ip;		/* ip/tcp hdr from most recent packet */
-};
+  union {
+    char csu_hdr[MAX_HDR];
+    struct ip csu_ip;		/* ip/tcp hdr from most recent packet */
+  } slcs_u;
+ };
+
+#define cs_ip slcs_u.csu_ip
+#define cs_hdr slcs_u.csu_hdr
 
 /*
  * all the state data for one serial line (we need one of these