diff --git a/src/tag/Rva2.cxx b/src/tag/Rva2.cxx
index 2291aa34d..53e34f957 100644
--- a/src/tag/Rva2.cxx
+++ b/src/tag/Rva2.cxx
@@ -133,7 +133,8 @@ rva2_apply_frame(ReplayGainInfo &replay_gain_info,
 }
 
 bool
-tag_rva2_parse(struct id3_tag *tag, ReplayGainInfo &replay_gain_info)
+tag_rva2_parse(const struct id3_tag *tag,
+	       ReplayGainInfo &replay_gain_info) noexcept
 {
 	bool found = false;
 
diff --git a/src/tag/Rva2.hxx b/src/tag/Rva2.hxx
index d30d2ad0f..acbdeff40 100644
--- a/src/tag/Rva2.hxx
+++ b/src/tag/Rva2.hxx
@@ -32,6 +32,7 @@ struct ReplayGainInfo;
  * @return true on success
  */
 bool
-tag_rva2_parse(id3_tag *tag, ReplayGainInfo &replay_gain_info);
+tag_rva2_parse(const struct id3_tag *tag,
+	       ReplayGainInfo &replay_gain_info) noexcept;
 
 #endif