diff --git a/include/xapo.idl b/include/xapo.idl
index 7b28ac9f439..841793d4fa5 100644
--- a/include/xapo.idl
+++ b/include/xapo.idl
@@ -20,6 +20,13 @@ import "unknwn.idl";
 
 #define XAPO_REGISTRATION_STRING_LENGTH 256
 
+cpp_quote("#define XAPO_FLAG_CHANNELS_MUST_MATCH 0x1")
+cpp_quote("#define XAPO_FLAG_FRAMERATE_MUST_MATCH 0x2")
+cpp_quote("#define XAPO_FLAG_BITSPERSAMPLE_MUST_MATCH 0x4")
+cpp_quote("#define XAPO_FLAG_BUFFERCOUNT_MUST_MATCH 0x8")
+cpp_quote("#define XAPO_FLAG_INPLACE_SUPPORTED 0x10")
+cpp_quote("#define XAPO_FLAG_INPLACE_REQUIRED 0x20")
+
 cpp_quote("#if 0")
 typedef struct WAVEFORMATEX
 {