diff --git a/RealmSwift/Aliases.swift b/RealmSwift/Aliases.swift
index 24d72621e3..25cb6804f0 100644
--- a/RealmSwift/Aliases.swift
+++ b/RealmSwift/Aliases.swift
@@ -94,10 +94,8 @@ extension ObjectBase {
         let token = RLMObjectNotificationToken()
         token.observe(self, keyPaths: keyPaths) { object, names, oldValues, newValues, error in
             assert(error == nil)
-            assumeOnActorExecutor(actor) { actor in
-                block(actor, .init(object: object as? T, names: names,
+            actor.invokeIsolated(block, .init(object: object as? T, names: names,
                         oldValues: oldValues, newValues: newValues))
-            }
         }
         await withTaskCancellationHandler(operation: token.registrationComplete,
                                           onCancel: { token.invalidate() })
diff --git a/RealmSwift/Impl/RealmCollectionImpl.swift b/RealmSwift/Impl/RealmCollectionImpl.swift
index 5957147b25..4ac3e34bb6 100644
--- a/RealmSwift/Impl/RealmCollectionImpl.swift
+++ b/RealmSwift/Impl/RealmCollectionImpl.swift
@@ -128,9 +128,7 @@ extension RealmCollectionImpl {
     ) async -> NotificationToken {
         await with(self, on: actor) { actor, collection in
             collection.observe(keyPaths: keyPaths, on: nil) { change in
-                assumeOnActorExecutor(actor) { actor in
-                    block(actor, change)
-                }
+                actor.invokeIsolated(block, change)
             }
         } ?? NotificationToken()
     }
diff --git a/RealmSwift/Map.swift b/RealmSwift/Map.swift
index 88274cefcd..4f5d48af25 100644
--- a/RealmSwift/Map.swift
+++ b/RealmSwift/Map.swift
@@ -607,9 +607,7 @@ public final class Map<Key: _MapKey, Value: RealmCollectionValue>: RLMSwiftColle
     ) async -> NotificationToken {
         await with(self, on: actor) { actor, collection in
             collection.observe(keyPaths: keyPaths, on: nil) { change in
-                assumeOnActorExecutor(actor) { actor in
-                    block(actor, change)
-                }
+                actor.invokeIsolated(block, change)
             }
         } ?? NotificationToken()
     }
diff --git a/RealmSwift/Projection.swift b/RealmSwift/Projection.swift
index 60a4101765..73e3b42f82 100644
--- a/RealmSwift/Projection.swift
+++ b/RealmSwift/Projection.swift
@@ -536,9 +536,7 @@ extension ProjectionObservable {
     ) async -> NotificationToken {
         await with(self, on: actor) { actor, obj in
             obj.observe(keyPaths: keyPaths, on: nil) { (change: ObjectChange<Self>) in
-                assumeOnActorExecutor(actor) { actor in
-                    block(actor, change)
-                }
+                actor.invokeIsolated(block, change)
             }
         } ?? NotificationToken()
     }
diff --git a/RealmSwift/SectionedResults.swift b/RealmSwift/SectionedResults.swift
index acbe569411..04cd203393 100644
--- a/RealmSwift/SectionedResults.swift
+++ b/RealmSwift/SectionedResults.swift
@@ -206,9 +206,7 @@ public extension RealmSectionedResult {
     ) async -> NotificationToken {
         await with(self, on: actor) { actor, collection in
             collection.observe(keyPaths: keyPaths, on: nil) { change in
-                assumeOnActorExecutor(actor) { actor in
-                    block(actor, change)
-                }
+                actor.invokeIsolated(block, change)
             }
         } ?? NotificationToken()
     }
diff --git a/RealmSwift/Util.swift b/RealmSwift/Util.swift
index d5b600db09..7a6e29df33 100644
--- a/RealmSwift/Util.swift
+++ b/RealmSwift/Util.swift
@@ -160,30 +160,43 @@ internal func logRuntimeIssue(_ message: StaticString) {
     }
 }
 
+@available(macOS 10.15, tvOS 13.0, iOS 13.0, watchOS 6.0, *)
 @_unavailableFromAsync
-internal func assumeOnMainActorExecutor<T>(_ operation: @MainActor () throws -> T,
-                                           file: StaticString = #fileID, line: UInt = #line
-) rethrows -> T {
+internal func assumeOnMainActorExecutor(_ operation: @MainActor () throws -> Void,
+                                        file: StaticString = #fileID, line: UInt = #line
+) rethrows {
+#if compiler(>=5.10)
+    // This is backdeployable in Xcode 15.3+, but not 15.1
+    try MainActor.assumeIsolated(operation)
+#else
     if #available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *) {
         return try MainActor.assumeIsolated(operation)
     }
 
     precondition(Thread.isMainThread, file: file, line: line)
     return try withoutActuallyEscaping(operation) { fn in
-        try unsafeBitCast(fn, to: (() throws -> T).self)()
+        try unsafeBitCast(fn, to: (() throws -> ()).self)()
     }
+#endif
 }
 
-@_unavailableFromAsync
 @available(macOS 10.15, tvOS 13.0, iOS 13.0, watchOS 6.0, *)
-internal func assumeOnActorExecutor<A: Actor, T>(_ actor: A,
-                                                 _ operation: (isolated A) throws -> T
-) rethrows -> T {
-    if #available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *) {
-        return try actor.assumeIsolated(operation)
-    }
+extension Actor {
+    @_unavailableFromAsync
+    internal func invokeIsolated<Ret, Arg>(_ operation: (isolated Self, Arg) throws -> Ret, _ arg: Arg,
+                                           file: StaticString = #fileID, line: UInt = #line
+    ) rethrows -> Ret {
+#if compiler(>=5.10)
+        // This is backdeployable in Xcode 15.3+, but not 15.1
+        preconditionIsolated(file: file, line: line)
+#else
+        if #available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *) {
+            preconditionIsolated(file: file, line: line)
+        }
+#endif
 
-    return try withoutActuallyEscaping(operation) { fn in
-        try unsafeBitCast(fn, to: ((A) throws -> T).self)(actor)
+        return try withoutActuallyEscaping(operation) { fn in
+            try unsafeBitCast(fn, to: ((Self, Arg) throws -> Ret).self)(self, arg)
+        }
     }
 }