diff --git a/editcap.c b/editcap.c
index b646167089..9a2d799cb0 100644
--- a/editcap.c
+++ b/editcap.c
@@ -1122,7 +1122,7 @@ process_new_idbs(wtap *wth, wtap_dumper *pdh, GArray *idbs_seen,
          * That mean that the abstract interface provided by libwiretap
          * involves WTAP_BLOCK_IF_ID_AND_INFO blocks.
          */
-        if (wtap_file_type_subtype_supports_block(wtap_dump_file_type_subtype(pdh),
+        if (pdh != NULL && wtap_file_type_subtype_supports_block(wtap_dump_file_type_subtype(pdh),
                                                   WTAP_BLOCK_IF_ID_AND_INFO) != BLOCK_NOT_SUPPORTED) {
             wtap_block_t if_data_copy;
 
@@ -1849,11 +1849,9 @@ main(int argc, char *argv[])
     while (wtap_read(wth, &read_rec, &read_buf, &read_err, &read_err_info, &data_offset)) {
         /*
          * XXX - what about non-packet records in the file after this?
-         * We can *probably* ignore IDBs after this point, as they
-         * presumably indicate that we weren't capturing on that
-         * interface at this point, but what about, for example, ISBs?
-         * (NRBs and DSBs are now written when wtap_dump_close() calls
-         * pcapng_dump_finish().)
+         * NRBs, DSBs, and ISBs are now written when wtap_dump_close() calls
+         * pcapng_dump_finish(), and we handle IDBs below, but what about
+         * custom blocks?
          */
         if (max_packet_number <= read_count)
             break;
@@ -2389,6 +2387,18 @@ main(int argc, char *argv[])
         }
     }
 
+    /*
+     * Process whatever IDBs we haven't seen yet.
+     */
+    if (!process_new_idbs(wth, pdh, idbs_seen, &write_err, &write_err_info)) {
+        cfile_write_failure_message(argv[ws_optind], filename,
+                                    write_err, write_err_info,
+                                    read_count,
+                                    out_file_type_subtype);
+        ret = DUMP_ERROR;
+        goto clean_exit;
+    }
+
     if (!wtap_dump_close(pdh, NULL, &write_err, &write_err_info)) {
         cfile_close_failure_message(filename, write_err, write_err_info);
         ret = WRITE_ERROR;
diff --git a/tshark.c b/tshark.c
index c12cbbdeb8..f5a8cbb3c3 100644
--- a/tshark.c
+++ b/tshark.c
@@ -3583,9 +3583,19 @@ process_cap_file_single_pass(capture_file *cf, wtap_dumper *pdh,
         }
         wtap_rec_reset(&rec);
     }
-    if (*err != 0 && status == PASS_SUCCEEDED) {
-        /* Error reading from the input file. */
-        status = PASS_READ_ERROR;
+    if (status == PASS_SUCCEEDED) {
+        if (*err != 0) {
+            /* Error reading from the input file. */
+            status = PASS_READ_ERROR;
+        } else {
+            /*
+             * Process whatever IDBs we haven't seen yet.
+             */
+            if (!process_new_idbs(cf->provider.wth, pdh, err, err_info)) {
+                *err_framenum = framenum;
+                status = PASS_WRITE_ERROR;
+            }
+        }
     }
 
     if (edt)
diff --git a/wiretap/merge.c b/wiretap/merge.c
index ed2f5d7b5d..0c3c919acf 100644
--- a/wiretap/merge.c
+++ b/wiretap/merge.c
@@ -1046,7 +1046,13 @@ merge_process_packets(wtap_dumper *pdh, const int file_type,
         cb->callback_func(MERGE_EVENT_DONE, count, in_files, in_file_count, cb->data);
 
     if (status == MERGE_OK || status == MERGE_USER_ABORTED) {
-        /* Check for any NRBs or DSBs read after the last packet records. */
+        /* Check for IDBs, NRBs, or DSBs read after the last packet records. */
+        if (wtap_file_type_subtype_supports_block(file_type,
+                                                  WTAP_BLOCK_IF_ID_AND_INFO) != BLOCK_NOT_SUPPORTED) {
+            if (!process_new_idbs(pdh, in_files, in_file_count, mode, idb_inf, err, err_info)) {
+                status = MERGE_ERR_CANT_WRITE_OUTFILE;
+            }
+        }
         if (nrb_combined) {
             for (guint j = 0; j < in_file_count; j++) {
                 in_file = &in_files[j];
@@ -1073,6 +1079,8 @@ merge_process_packets(wtap_dumper *pdh, const int file_type,
                 }
             }
         }
+    }
+    if (status == MERGE_OK || status == MERGE_USER_ABORTED) {
         if (!wtap_dump_close(pdh, NULL, err, err_info))
             status = MERGE_ERR_CANT_CLOSE_OUTFILE;
     } else {