diff --git a/Packages/.gitignore b/Packages/.gitignore
index 252bcc9e..57171bef 100644
--- a/Packages/.gitignore
+++ b/Packages/.gitignore
@@ -2,4 +2,4 @@
 !com.vrchat.core.*/
 com.vrchat.*/
 !nadena.dev.*/
-*.zip
\ No newline at end of file
+*.zip
diff --git a/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs b/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs
index 529000ce..0cc51516 100644
--- a/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs
+++ b/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs
@@ -33,11 +33,7 @@ using System.Reflection;
 
 namespace nadena.dev.modular_avatar.core
 {
-    /**
-     * This class is public for the benefit of the Editor namespace classes, but is not a stable API and may change
-     * on patch releases.
-     */
-    public static class RuntimeUtil
+    internal static class RuntimeUtil
     {
         // Initialized in Util
         public static Action<Action> delayCall = (_) => { };
@@ -156,4 +152,4 @@ namespace nadena.dev.modular_avatar.core
             OnHierarchyChanged?.Invoke();
         }
     }
-}
\ No newline at end of file
+}
diff --git a/Packages/nadena.dev.modular-avatar/Runtime/assembly-info.cs b/Packages/nadena.dev.modular-avatar/Runtime/assembly-info.cs
new file mode 100644
index 00000000..77916945
--- /dev/null
+++ b/Packages/nadena.dev.modular-avatar/Runtime/assembly-info.cs
@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly:InternalsVisibleTo("nadena.dev.modular-avatar.core.editor")]
diff --git a/Packages/nadena.dev.modular-avatar/Runtime/assembly-info.cs.meta b/Packages/nadena.dev.modular-avatar/Runtime/assembly-info.cs.meta
new file mode 100644
index 00000000..82128637
--- /dev/null
+++ b/Packages/nadena.dev.modular-avatar/Runtime/assembly-info.cs.meta
@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 3921b79c7fa94c058aefa7d765c11e99
+timeCreated: 1673178956
\ No newline at end of file