diff --git a/src/opus.cc b/src/opus.cc
index 971ab61..06b9be8 100644
--- a/src/opus.cc
+++ b/src/opus.cc
@@ -34,6 +34,9 @@
 #define le32toh(x) OSSwapLittleToHostInt32(x)
 #endif
 
+/**
+ * \todo Use RAII. Here the allocated objects are not even properly freed on error.
+ */
 int ot::parse_tags(const char *data, long len, opus_tags *tags)
 {
 	long pos;
@@ -70,10 +73,8 @@ int ot::parse_tags(const char *data, long len, opus_tags *tags)
 		if (pos > len)
 			return -1;
 	}
-
-	if (pos < len)
-		fprintf(stderr, "warning: %ld unused bytes at the end of the OpusTags packet\n", len - pos);
-
+	// Extra data
+	tags->extra_data = ot::string_view{data + pos, static_cast<size_t>(len - pos)};
 	return 0;
 }
 
@@ -88,6 +89,7 @@ int ot::render_tags(opus_tags *tags, ogg_packet *op)
 	uint32_t i;
 	for (i=0; i<tags->count; i++)
 		len += 4 + tags->lengths[i];
+	len += tags->extra_data.size;
 	op->bytes = len;
 	char *data = static_cast<char*>(malloc(len));
 	if (!data)
@@ -108,6 +110,7 @@ int ot::render_tags(opus_tags *tags, ogg_packet *op)
 		memcpy(data+4, tags->comment[i], tags->lengths[i]);
 		data += 4 + tags->lengths[i];
 	}
+	memcpy(data, tags->extra_data.data, tags->extra_data.size);
 	return 0;
 }
 
diff --git a/src/opustags.h b/src/opustags.h
index 0b3a752..d68aa4b 100644
--- a/src/opustags.h
+++ b/src/opustags.h
@@ -9,6 +9,14 @@
 
 namespace ot {
 
+/**
+ * Non-owning string, similar to what std::string_view is in C++17.
+ */
+struct string_view {
+	const char *data;
+	size_t size;
+};
+
 /**
  * \defgroup ogg Ogg
  * \brief Helpers to work with libogg.
@@ -29,8 +37,6 @@ int write_page(ogg_page *og, FILE *stream);
 
 /**
  * Represent all the data in an OpusTags packet.
- *
- * \todo The comment list may be followed by arbitrary binary data, which we should keep here.
  */
 struct opus_tags {
 	uint32_t vendor_length;
@@ -38,6 +44,18 @@ struct opus_tags {
 	uint32_t count;
 	uint32_t *lengths;
 	const char **comment;
+	/**
+	 * According to RFC 7845:
+	 * > Immediately following the user comment list, the comment header MAY contain
+	 * > zero-padding or other binary data that is not specified here.
+	 *
+	 * The first byte is supposed to indicate whether this data should be kept or not, but let's
+	 * assume it's here for a reason and always keep it. Better safe than sorry.
+	 *
+	 * In the future, we could add options to manipulate this data: view it, edit it, truncate
+	 * it if it's marked as padding, truncate it unconditionally.
+	 */
+	string_view extra_data;
 };
 
 int parse_tags(const char *data, long len, opus_tags *tags);
diff --git a/t/unit.cc b/t/unit.cc
index c405353..11c40fc 100644
--- a/t/unit.cc
+++ b/t/unit.cc
@@ -54,6 +54,8 @@ static bool parse_standard()
 		throw failure("bad title comment");
 	if (memcmp(tags.comment[1], "ARTIST=Bar", tags.lengths[1]) != 0)
 		throw failure("bad artist comment");
+	if (tags.extra_data.size != 0)
+		throw failure("found mysterious padding data");
 	ot::free_tags(&tags);
 	return true;
 }
@@ -94,6 +96,11 @@ static bool recode_padding()
 	int rc = ot::parse_tags(padded_OpusTags.data(), padded_OpusTags.size(), &tags);
 	if (rc != 0)
 		throw failure("ot::parse_tags did not return 0");
+	if (tags.extra_data.size != 6)
+		throw failure("unexpected amount of extra bytes");
+	if (memcmp(tags.extra_data.data, "\0hello", 6) != 0)
+		throw failure("corrupted extra data");
+	// recode the packet and ensure it's exactly the same
 	ogg_packet packet;
 	rc = ot::render_tags(&tags, &packet);
 	if (packet.bytes < padded_OpusTags.size())