diff --git a/src/hydro/Gizmo/MFM/hydro_part.h b/src/hydro/Gizmo/MFM/hydro_part.h
index 1f6f3c71473e4fdd3851b4238839a1b1dccdb877..81687e71b5702c830287a234acde0ea4c0694e3b 100644
--- a/src/hydro/Gizmo/MFM/hydro_part.h
+++ b/src/hydro/Gizmo/MFM/hydro_part.h
@@ -178,6 +178,9 @@ struct part {
   /*! Time-step length */
   timebin_t time_bin;
 
+  /*! Tree-depth at which size / 2 <= h * gamma < size */
+  char depth_h;
+
   /*! Time-step limiter information */
   struct timestep_limiter_data limiter_data;
 
diff --git a/src/hydro/Gizmo/MFV/hydro_part.h b/src/hydro/Gizmo/MFV/hydro_part.h
index e734c6ca9d5abf182627708120e9b9ffcf7de65f..8e2f38e4e457f833620426a1fc08c4d3161bbb3e 100644
--- a/src/hydro/Gizmo/MFV/hydro_part.h
+++ b/src/hydro/Gizmo/MFV/hydro_part.h
@@ -182,6 +182,9 @@ struct part {
   /*! Time-step length */
   timebin_t time_bin;
 
+  /*! Tree-depth at which size / 2 <= h * gamma < size */
+  char depth_h;
+
   /*! Time-step limiter information */
   struct timestep_limiter_data limiter_data;