diff --git a/wiretap/iptrace.c b/wiretap/iptrace.c
index ab2b05139d..e87f74c6db 100644
--- a/wiretap/iptrace.c
+++ b/wiretap/iptrace.c
@@ -1,6 +1,6 @@
 /* iptrace.c
  *
- * $Id: iptrace.c,v 1.13 1999/10/05 07:06:05 guy Exp $
+ * $Id: iptrace.c,v 1.14 1999/10/06 03:29:36 guy Exp $
  *
  * Wiretap Library
  * Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
@@ -132,5 +132,18 @@ static int iptrace_read(wtap *wth, int *err)
 		*err = WTAP_ERR_BAD_RECORD;
 		return -1;
 	}
+
+	/* If the per-file encapsulation isn't known, set it to this
+	   packet's encapsulation.
+
+	   If it *is* known, and it isn't this packet's encapsulation,
+	   set it to WTAP_ENCAP_PER_PACKET, as this file doesn't
+	   have a single encapsulation for all packets in the file. */
+	if (wth->file_encap == WTAP_ENCAP_UNKNOWN)
+		wth->file_encap = wth->phdr.pkt_encap;
+	else {
+		if (wth->file_encap != wth->phdr.pkt_encap)
+			wth->file_encap= WTAP_ENCAP_PER_PACKET;
+	}
 	return data_offset;
 }
diff --git a/wiretap/wtap.c b/wiretap/wtap.c
index 959878ed35..bc293567af 100644
--- a/wiretap/wtap.c
+++ b/wiretap/wtap.c
@@ -1,6 +1,6 @@
 /* wtap.c
  *
- * $Id: wtap.c,v 1.24 1999/10/05 07:22:53 guy Exp $
+ * $Id: wtap.c,v 1.25 1999/10/06 03:29:35 guy Exp $
  *
  * Wiretap Library
  * Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
@@ -51,6 +51,11 @@ int wtap_snapshot_length(wtap *wth)
 	return wth->snapshot_length;
 }
 
+int wtap_file_encap(wtap *wth)
+{
+	return wth->file_encap;
+}
+
 const char *wtap_file_type_string(wtap *wth)
 {
 	switch (wth->file_type) {
diff --git a/wiretap/wtap.h b/wiretap/wtap.h
index 22e76a611c..5ca5d8edfb 100644
--- a/wiretap/wtap.h
+++ b/wiretap/wtap.h
@@ -1,6 +1,6 @@
 /* wtap.h
  *
- * $Id: wtap.h,v 1.42 1999/10/05 07:06:08 guy Exp $
+ * $Id: wtap.h,v 1.43 1999/10/06 03:29:36 guy Exp $
  *
  * Wiretap Library
  * Copyright (c) 1998 by Gilbert Ramirez <gram@verdict.uthscsa.edu>
@@ -31,6 +31,8 @@
  * "wtap_dump_fd_open()" to indicate that there is no single encapsulation
  * type for all packets in the file; this may cause those routines to
  * fail if the capture file format being written can't support that.
+ * It's also returned by "wtap_file_encap()" for capture files that
+ * don't have a single encapsulation type for all packets in the file.
  *
  * WTAP_ENCAP_UNKNOWN is returned by "wtap_pcap_encap_to_wtap_encap()"
  * if it's handed an unknown encapsulation.
@@ -345,6 +347,7 @@ FILE* wtap_file(wtap *wth);
 int wtap_fd(wtap *wth);
 int wtap_snapshot_length(wtap *wth); /* per file */
 int wtap_file_type(wtap *wth);
+int wtap_file_encap(wtap *wth);
 const char *wtap_file_type_string(wtap *wth);
 const char *wtap_strerror(int err);
 void wtap_close(wtap *wth);