diff --git a/src/cli.cc b/src/cli.cc
index a5601a4..595066b 100644
--- a/src/cli.cc
+++ b/src/cli.cc
@@ -402,7 +402,7 @@ static void output_cover(const ot::opus_tags& tags, const ot::options &opt)
 {
 	std::optional<ot::picture> cover = extract_cover(tags);
 	if (!cover) {
-		fputs("warning: no cover found.\n", stderr);
+		fputs("warning: No cover found.\n", stderr);
 		return;
 	}
 
diff --git a/src/opus.cc b/src/opus.cc
index 36b4772..df36bad 100644
--- a/src/opus.cc
+++ b/src/opus.cc
@@ -149,6 +149,9 @@ ot::picture::picture(std::string block)
 	picture_data = std::string_view(reinterpret_cast<const char*>(bytes + pic_offset + 4), pic_size);
 }
 
+/**
+ * \todo Take into account the picture types (first 4 bytes of the tag value).
+ */
 std::optional<ot::picture> ot::extract_cover(const ot::opus_tags& tags)
 {
 	static const std::string_view prefix = "METADATA_BLOCK_PICTURE="sv;
@@ -157,6 +160,11 @@ std::optional<ot::picture> ot::extract_cover(const ot::opus_tags& tags)
 	if (cover_tag == tags.comments.end())
 		return {}; // No cover art.
 
+	auto extra_cover_tag = std::find_if(std::next(cover_tag), tags.comments.end(), is_cover);
+	if (extra_cover_tag != tags.comments.end())
+		fputs("warning: Found multiple covers; only the first will be extracted."
+		              " Please report your use case if you need a finer selection.\n", stderr);
+
 	std::string_view cover_value = *cover_tag;
 	cover_value.remove_prefix(prefix.size());
 	return picture(decode_base64(cover_value));
diff --git a/t/opus.cc b/t/opus.cc
index cb83bea..fdeed6b 100644
--- a/t/opus.cc
+++ b/t/opus.cc
@@ -148,7 +148,7 @@ static void extract_cover()
 		"\x00\x00\x00\x0C" "Picture data";
 
 	ot::opus_tags tags;
-	tags.comments.push_front("METADATA_BLOCK_PICTURE=" + ot::encode_base64(picture_data));
+	tags.comments = { "METADATA_BLOCK_PICTURE=" + ot::encode_base64(picture_data) };
 	std::optional<ot::picture> cover = ot::extract_cover(tags);
 	if (!cover)
 		throw failure("could not extract the cover");
@@ -158,7 +158,7 @@ static void extract_cover()
 		throw failure("bad extracted picture data");
 
 	std::string_view truncated_data = picture_data.substr(0, picture_data.size() - 1);
-	tags.comments.push_front("METADATA_BLOCK_PICTURE=" + ot::encode_base64(truncated_data));
+	tags.comments = { "METADATA_BLOCK_PICTURE=" + ot::encode_base64(truncated_data) };
 	try {
 		ot::extract_cover(tags);
 		throw failure("accepted a bad picture block");