diff --git a/debian/libwiretap0.symbols b/debian/libwiretap0.symbols
index da7dcc1381..16a622d8a4 100644
--- a/debian/libwiretap0.symbols
+++ b/debian/libwiretap0.symbols
@@ -21,7 +21,7 @@ libwiretap.so.0 libwiretap0 #MINVER#
  register_pcapng_option_handler@Base 1.99.2
  wtap_add_generated_idb@Base 3.3.0
  wtap_addrinfo_list_empty@Base 2.5.0
- wtap_block_add_custom_option@Base 2.1.2
+ wtap_block_add_structured_option@Base 3.5.0
  wtap_block_add_ipv4_option@Base 2.1.2
  wtap_block_add_ipv6_option@Base 2.1.2
  wtap_block_add_string_option@Base 2.1.2
@@ -33,7 +33,7 @@ libwiretap.so.0 libwiretap0 #MINVER#
  wtap_block_create@Base 2.1.2
  wtap_block_foreach_option@Base 2.1.2
  wtap_block_free@Base 2.1.2
- wtap_block_get_custom_option_value@Base 2.1.2
+ wtap_block_get_structured_option_value@Base 3.5.0
  wtap_block_get_ipv4_option_value@Base 2.1.2
  wtap_block_get_ipv6_option_value@Base 2.1.2
  wtap_block_get_mandatory_data@Base 2.1.2
@@ -44,7 +44,7 @@ libwiretap.so.0 libwiretap0 #MINVER#
  wtap_block_make_copy@Base 3.3.2
  wtap_block_remove_nth_option_instance@Base 2.2.0
  wtap_block_remove_option@Base 2.2.0
- wtap_block_set_custom_option_value@Base 2.1.2
+ wtap_block_set_structured_option_value@Base 3.5.0
  wtap_block_set_ipv4_option_value@Base 2.1.2
  wtap_block_set_ipv6_option_value@Base 2.1.2
  wtap_block_set_nth_string_option_value@Base 2.1.2
diff --git a/ui/summary.c b/ui/summary.c
index 868528583a..565bb86307 100644
--- a/ui/summary.c
+++ b/ui/summary.c
@@ -171,7 +171,7 @@ summary_fill_in(capture_file *cf, summary_tally *st)
   for (i = 0; i < idb_info->interface_data->len; i++) {
     wtapng_if_descr = g_array_index(idb_info->interface_data, wtap_block_t, i);
     wtapng_if_descr_mand = (wtapng_if_descr_mandatory_t*)wtap_block_get_mandatory_data(wtapng_if_descr);
-    if (wtap_block_get_custom_option_value(wtapng_if_descr, OPT_IDB_FILTER, (void**)&if_filter) == WTAP_OPTTYPE_SUCCESS) {
+    if (wtap_block_get_structured_option_value(wtapng_if_descr, OPT_IDB_FILTER, (void**)&if_filter) == WTAP_OPTTYPE_SUCCESS) {
       iface.cfilter = g_strdup(if_filter->if_filter_str);
     } else {
       iface.cfilter = NULL;
diff --git a/wiretap/erf.c b/wiretap/erf.c
index b391a2d1f5..8804f450f8 100644
--- a/wiretap/erf.c
+++ b/wiretap/erf.c
@@ -1109,7 +1109,7 @@ static void erf_write_wtap_option_to_interface_tag(wtap_block_t block _U_,
       {
         wtapng_if_descr_filter_t *filter;
         tag_ptr->type = 0xF800;
-        filter = (wtapng_if_descr_filter_t*)&optval->customval;
+        filter = (wtapng_if_descr_filter_t*)&optval->structuredval;
         if(filter->if_filter_str) {
           tag_ptr->type = ERF_META_TAG_filter;
           tag_ptr->value = (guint8*)g_strdup(filter->if_filter_str);
@@ -2841,7 +2841,7 @@ static int populate_interface_info(erf_t *erf_priv, wtap *wth, union wtap_pseudo
         break;
       case ERF_META_TAG_filter:
         if_filter.if_filter_str = g_strndup((gchar*) tag.value, tag.length);
-        wtap_block_add_custom_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
+        wtap_block_add_structured_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
         g_free(if_filter.if_filter_str);
         if_info->set_flags.filter = 1;
         break;
@@ -2867,7 +2867,7 @@ static int populate_interface_info(erf_t *erf_priv, wtap *wth, union wtap_pseudo
     if (state->if_map->module_filter_str) {
       /* Duplicate because might use with multiple interfaces */
       if_filter.if_filter_str = state->if_map->module_filter_str;
-      wtap_block_add_custom_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
+      wtap_block_add_structured_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
       /*
        * Don't set flag because stream is more specific than module.
        */
@@ -2875,7 +2875,7 @@ static int populate_interface_info(erf_t *erf_priv, wtap *wth, union wtap_pseudo
       /* TODO: display separately? Note that we could have multiple captures
        * from multiple hosts in the file */
       if_filter.if_filter_str = state->if_map->capture_filter_str;
-      wtap_block_add_custom_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
+      wtap_block_add_structured_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
     }
   }
 
@@ -3012,7 +3012,7 @@ static int populate_stream_info(erf_t *erf_priv _U_, wtap *wth, union wtap_pseud
           /* Override only if not set */
           if (!if_info->set_flags.filter) {
             if_filter.if_filter_str = g_strndup((gchar*) tag.value, tag.length);
-            wtap_block_add_custom_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
+            wtap_block_add_structured_option(int_data, OPT_IDB_FILTER, &if_filter, sizeof if_filter);
             g_free(if_filter.if_filter_str);
             if_info->set_flags.filter = 1;
           }
diff --git a/wiretap/pcapng.c b/wiretap/pcapng.c
index b19f625ae4..019bf17084 100644
--- a/wiretap/pcapng.c
+++ b/wiretap/pcapng.c
@@ -950,7 +950,7 @@ pcapng_read_if_descr_block(wtap *wth, FILE_T fh, pcapng_block_header_t *bh,
                         if_filter.if_filter_bpf_bytes = option_content+1;
                     }
                     /* Fails with multiple options; we silently ignore the failure */
-                    wtap_block_add_custom_option(wblock->block, oh.option_code, &if_filter, sizeof if_filter);
+                    wtap_block_add_structured_option(wblock->block, oh.option_code, &if_filter, sizeof if_filter);
                     g_free(if_filter.if_filter_str);
                 } else {
                     pcapng_debug("pcapng_read_if_descr_block: if_filter length %u seems strange", oh.option_length);
@@ -4541,7 +4541,7 @@ static void compute_idb_option_size(wtap_block_t block _U_, guint option_id, wta
         break;
     case OPT_IDB_FILTER:
         {
-            wtapng_if_descr_filter_t* filter = (wtapng_if_descr_filter_t*)optval->customval.data;
+            wtapng_if_descr_filter_t* filter = (wtapng_if_descr_filter_t*)optval->structuredval.data;
             guint32 pad;
             if (filter->if_filter_str != NULL) {
                 size = (guint32)(strlen(filter->if_filter_str) + 1) & 0xffff;
@@ -4631,7 +4631,7 @@ static void write_wtap_idb_option(wtap_block_t block _U_, guint option_id, wtap_
         break;
     case OPT_IDB_FILTER:
         {
-            wtapng_if_descr_filter_t* filter = (wtapng_if_descr_filter_t*)optval->customval.data;
+            wtapng_if_descr_filter_t* filter = (wtapng_if_descr_filter_t*)optval->structuredval.data;
             guint32 size, pad;
             if (filter->if_filter_str != NULL) {
                 size = (guint32)(strlen(filter->if_filter_str) + 1) & 0xffff;
diff --git a/wiretap/wtap.c b/wiretap/wtap.c
index b5427d34e3..ff4479f68a 100644
--- a/wiretap/wtap.c
+++ b/wiretap/wtap.c
@@ -365,7 +365,7 @@ wtap_get_debug_if_descr(const wtap_block_t if_descr,
 				line_end);
 	}
 
-	if (wtap_block_get_custom_option_value(if_descr, OPT_IDB_FILTER, (void**)&if_filter) == WTAP_OPTTYPE_SUCCESS) {
+	if (wtap_block_get_structured_option_value(if_descr, OPT_IDB_FILTER, (void**)&if_filter) == WTAP_OPTTYPE_SUCCESS) {
 		g_string_append_printf(info,
 				"%*cFilter string = %s%s", indent, ' ',
 				if_filter->if_filter_str ? if_filter->if_filter_str : "NONE",
diff --git a/wiretap/wtap_opttypes.c b/wiretap/wtap_opttypes.c
index 9a5f66d9e3..a86a93a804 100644
--- a/wiretap/wtap_opttypes.c
+++ b/wiretap/wtap_opttypes.c
@@ -36,19 +36,19 @@ typedef struct {
     GArray *options;                 /**< array of known options */
 } wtap_blocktype_t;
 
-typedef void *(*wtap_opttype_dup_custom_func)(void* src);
-typedef void (*wtap_opttype_free_custom_func)(void* data);
+typedef void *(*wtap_opttype_dup_structured_func)(void* src);
+typedef void (*wtap_opttype_free_structured_func)(void* data);
 
 /*
  * Structure describing a type of option.
  */
 typedef struct {
-    const char *name;                        /**< name of option */
-    const char *description;                 /**< human-readable description of option */
-    wtap_opttype_e data_type;                /**< data type of that option */
-    guint flags;                             /**< flags for the option */
-    wtap_opttype_dup_custom_func dup_func;   /**< function to duplicate custom option data */
-    wtap_opttype_free_custom_func free_func; /**< function to free custom option data */
+    const char *name;                            /**< name of option */
+    const char *description;                     /**< human-readable description of option */
+    wtap_opttype_e data_type;                    /**< data type of that option */
+    guint flags;                                 /**< flags for the option */
+    wtap_opttype_dup_structured_func dup_func;   /**< function to duplicate structured option data */
+    wtap_opttype_free_structured_func free_func; /**< function to free structured option data */
 } wtap_opttype_t;
 
 /* Flags */
@@ -204,9 +204,9 @@ static void wtap_block_free_option(wtap_block_t block, wtap_option_t *opt)
         g_free(opt->value.stringval);
         break;
 
-    case WTAP_OPTTYPE_CUSTOM:
-        opttype->free_func(opt->value.customval.data);
-        g_free(opt->value.customval.data);
+    case WTAP_OPTTYPE_STRUCTURED:
+        opttype->free_func(opt->value.structuredval.data);
+        g_free(opt->value.structuredval.data);
         break;
 
     default:
@@ -298,8 +298,8 @@ wtap_block_copy(wtap_block_t dest_block, wtap_block_t src_block)
             wtap_block_add_string_option(dest_block, src_opt->option_id, src_opt->value.stringval, strlen(src_opt->value.stringval));
             break;
 
-        case WTAP_OPTTYPE_CUSTOM:
-            wtap_block_add_custom_option(dest_block, src_opt->option_id, src_opt->value.customval.data, src_opt->value.customval.size);
+        case WTAP_OPTTYPE_STRUCTURED:
+            wtap_block_add_structured_option(dest_block, src_opt->option_id, src_opt->value.structuredval.data, src_opt->value.structuredval.size);
             break;
         }
     }
@@ -753,50 +753,50 @@ wtap_block_get_nth_string_option_value(wtap_block_t block, guint option_id, guin
 }
 
 wtap_opttype_return_val
-wtap_block_add_custom_option(wtap_block_t block, guint option_id, void *value, size_t value_size)
+wtap_block_add_structured_option(wtap_block_t block, guint option_id, void *value, size_t value_size)
 {
     wtap_opttype_return_val ret;
     wtap_option_t *opt;
     wtap_opttype_t *opttype;
 
-    ret = wtap_block_add_option_common(block, option_id, WTAP_OPTTYPE_CUSTOM, &opt);
+    ret = wtap_block_add_option_common(block, option_id, WTAP_OPTTYPE_STRUCTURED, &opt);
     if (ret != WTAP_OPTTYPE_SUCCESS)
         return ret;
     opttype = &g_array_index(block->info->options, wtap_opttype_t, opt->option_id);
-    opt->value.customval.size = (guint)value_size;
-    opt->value.customval.data = opttype->dup_func(value);
+    opt->value.structuredval.size = (guint)value_size;
+    opt->value.structuredval.data = opttype->dup_func(value);
     return WTAP_OPTTYPE_SUCCESS;
 }
 
 wtap_opttype_return_val
-wtap_block_get_custom_option_value(wtap_block_t block, guint option_id, void** value)
+wtap_block_get_structured_option_value(wtap_block_t block, guint option_id, void** value)
 {
     wtap_opttype_return_val ret;
     wtap_optval_t *optval;
 
-    ret = wtap_block_get_option_common(block, option_id, WTAP_OPTTYPE_CUSTOM, &optval);
+    ret = wtap_block_get_option_common(block, option_id, WTAP_OPTTYPE_STRUCTURED, &optval);
     if (ret != WTAP_OPTTYPE_SUCCESS)
         return ret;
-    *value = optval->customval.data;
+    *value = optval->structuredval.data;
     return WTAP_OPTTYPE_SUCCESS;
 }
 
 wtap_opttype_return_val
-wtap_block_set_custom_option_value(wtap_block_t block, guint option_id, void *value)
+wtap_block_set_structured_option_value(wtap_block_t block, guint option_id, void *value)
 {
     wtap_opttype_return_val ret;
     wtap_optval_t *optval;
     void *prev_value;
 
-    ret = wtap_block_get_option_common(block, option_id, WTAP_OPTTYPE_CUSTOM, &optval);
+    ret = wtap_block_get_option_common(block, option_id, WTAP_OPTTYPE_STRUCTURED, &optval);
     if (ret != WTAP_OPTTYPE_SUCCESS)
         return ret;
-    prev_value = optval->customval.data;
+    prev_value = optval->structuredval.data;
     /*
      * XXX - a custom value can be a structure that points to other data,
      * but we're doing a shallow copy here.
      */
-    optval->customval.data = g_memdup(value, optval->customval.size);
+    optval->structuredval.data = g_memdup(value, optval->structuredval.size);
     /* Free after memory is duplicated in case structure was manipulated with a "get then set" */
     g_free(prev_value);
 
@@ -1081,7 +1081,7 @@ void wtap_opttypes_initialize(void)
     static wtap_opttype_t if_filter = {
         "filter",
         "IDB Filter",
-        WTAP_OPTTYPE_CUSTOM,
+        WTAP_OPTTYPE_STRUCTURED,
         0,
         idb_filter_dup,
         idb_filter_free
diff --git a/wiretap/wtap_opttypes.h b/wiretap/wtap_opttypes.h
index ab246dfc6f..c5d7112c68 100644
--- a/wiretap/wtap_opttypes.h
+++ b/wiretap/wtap_opttypes.h
@@ -144,7 +144,7 @@ typedef enum {
     WTAP_OPTTYPE_STRING,
     WTAP_OPTTYPE_IPv4,
     WTAP_OPTTYPE_IPv6,
-    WTAP_OPTTYPE_CUSTOM
+    WTAP_OPTTYPE_STRUCTURED
 } wtap_opttype_e;
 
 typedef enum {
@@ -156,7 +156,7 @@ typedef enum {
     WTAP_OPTTYPE_ALREADY_EXISTS = -5
 } wtap_opttype_return_val;
 
-struct wtap_opttype_custom
+struct wtap_opttype_structured
 {
     void* data;
     guint size;
@@ -171,7 +171,7 @@ typedef union {
     guint32 ipv4val;    /* network byte order */
     ws_in6_addr ipv6val;
     char *stringval;
-    struct wtap_opttype_custom customval;
+    struct wtap_opttype_structured structuredval;
 } wtap_optval_t;
 
 /*
@@ -456,7 +456,7 @@ wtap_block_get_nth_string_option_value(wtap_block_t block, guint option_id, guin
  * error code otherwise
  */
 WS_DLL_PUBLIC wtap_opttype_return_val
-wtap_block_add_custom_option(wtap_block_t block, guint option_id, void* value, size_t value_size);
+wtap_block_add_structured_option(wtap_block_t block, guint option_id, void* value, size_t value_size);
 
 /** Set a "custom" option value in a block
  *
@@ -467,7 +467,7 @@ wtap_block_add_custom_option(wtap_block_t block, guint option_id, void* value, s
  * error code otherwise
  */
 WS_DLL_PUBLIC wtap_opttype_return_val
-wtap_block_set_custom_option_value(wtap_block_t block, guint option_id, void* value);
+wtap_block_set_structured_option_value(wtap_block_t block, guint option_id, void* value);
 
 /** Get a "custom" option value from a block
  *
@@ -478,7 +478,7 @@ wtap_block_set_custom_option_value(wtap_block_t block, guint option_id, void* va
  * error code otherwise
  */
 WS_DLL_PUBLIC wtap_opttype_return_val
-wtap_block_get_custom_option_value(wtap_block_t block, guint option_id, void** value) G_GNUC_WARN_UNUSED_RESULT;
+wtap_block_get_structured_option_value(wtap_block_t block, guint option_id, void** value) G_GNUC_WARN_UNUSED_RESULT;
 
 /** Remove an option from a block
  *