diff --git a/shared/FlowDef.hpp b/shared/FlowDef.hpp
index ffd7a1f..cf42119 100644
--- a/shared/FlowDef.hpp
+++ b/shared/FlowDef.hpp
@@ -63,8 +63,9 @@ inline std::string make_audio_flow_def(
         {"parents",     json::array()},
         {"grain_rate",  {{"numerator", grain_rate_num}, {"denominator", grain_rate_den}}},
         {"sample_rate", {{"numerator", sample_rate},    {"denominator", 1}}},
-        {"channels",    ch_arr},
-        {"bit_depth",   bit_depth},
+        {"channels",       ch_arr},   // NMOS IS-04 metadata (ignored by MXL)
+        {"channel_count",  channels},  // MXL uses this for grain buffer geometry
+        {"bit_depth",      bit_depth}, // must be 32 or 64
         {"tags", {
             {"urn:x-nmos:tag:grouphint/v1.0", json::array({label + ":Audio"})}
         }},