diff --git a/build.sbt b/build.sbt
index 82a522f7a7..679df2d278 100644
--- a/build.sbt
+++ b/build.sbt
@@ -648,7 +648,10 @@ lazy val core = crossProject(JSPlatform, JVMPlatform, NativePlatform)
       ProblemFilters.exclude[IncompatibleResultTypeProblem](
         "cats.effect.unsafe.TimerSkipList.insert"),
       ProblemFilters.exclude[IncompatibleResultTypeProblem](
-        "cats.effect.unsafe.WorkerThread.sleep")
+        "cats.effect.unsafe.WorkerThread.sleep"),
+      // #3787, internal utility that was no longer needed
+      ProblemFilters.exclude[MissingClassProblem]("cats.effect.Thunk"),
+      ProblemFilters.exclude[MissingClassProblem]("cats.effect.Thunk$")
     ) ++ {
       if (tlIsScala3.value) {
         // Scala 3 specific exclusions
diff --git a/core/jvm/src/main/scala/cats/effect/IOCompanionPlatform.scala b/core/jvm/src/main/scala/cats/effect/IOCompanionPlatform.scala
index cf3a5303ac..ad9d75c8b7 100644
--- a/core/jvm/src/main/scala/cats/effect/IOCompanionPlatform.scala
+++ b/core/jvm/src/main/scala/cats/effect/IOCompanionPlatform.scala
@@ -47,14 +47,14 @@ private[effect] abstract class IOCompanionPlatform { this: IO.type =>
    * Implements [[cats.effect.kernel.Sync.blocking]].
    */
   def blocking[A](thunk: => A): IO[A] = {
-    val fn = Thunk.asFunction0(thunk)
+    val fn = () => thunk
     Blocking(TypeBlocking, fn, Tracing.calculateTracingEvent(fn.getClass))
   }
 
   // this cannot be marked private[effect] because of static forwarders in Java
   @deprecated("use interruptible / interruptibleMany instead", "3.3.0")
   def interruptible[A](many: Boolean, thunk: => A): IO[A] = {
-    val fn = Thunk.asFunction0(thunk)
+    val fn = () => thunk
     Blocking(
       if (many) TypeInterruptibleMany else TypeInterruptibleOnce,
       fn,
@@ -80,7 +80,7 @@ private[effect] abstract class IOCompanionPlatform { this: IO.type =>
    * Implements [[cats.effect.kernel.Sync.interruptible[A](thunk:=>A):*]]
    */
   def interruptible[A](thunk: => A): IO[A] = {
-    val fn = Thunk.asFunction0(thunk)
+    val fn = () => thunk
     Blocking(TypeInterruptibleOnce, fn, Tracing.calculateTracingEvent(fn.getClass))
   }
 
@@ -104,7 +104,7 @@ private[effect] abstract class IOCompanionPlatform { this: IO.type =>
    * Implements [[cats.effect.kernel.Sync!.interruptibleMany]]
    */
   def interruptibleMany[A](thunk: => A): IO[A] = {
-    val fn = Thunk.asFunction0(thunk)
+    val fn = () => thunk
     Blocking(TypeInterruptibleMany, fn, Tracing.calculateTracingEvent(fn.getClass))
   }
 
diff --git a/core/shared/src/main/scala/cats/effect/IO.scala b/core/shared/src/main/scala/cats/effect/IO.scala
index 372630f7bb..ea520aa21f 100644
--- a/core/shared/src/main/scala/cats/effect/IO.scala
+++ b/core/shared/src/main/scala/cats/effect/IO.scala
@@ -1130,7 +1130,7 @@ object IO extends IOCompanionPlatform with IOLowPriorityImplicits {
    * Any exceptions thrown by the effect will be caught and sequenced into the `IO`.
    */
   def delay[A](thunk: => A): IO[A] = {
-    val fn = Thunk.asFunction0(thunk)
+    val fn = () => thunk
     Delay(fn, Tracing.calculateTracingEvent(fn))
   }
 
diff --git a/core/shared/src/main/scala/cats/effect/Thunk.scala b/core/shared/src/main/scala/cats/effect/Thunk.scala
deleted file mode 100644
index d60a39a080..0000000000
--- a/core/shared/src/main/scala/cats/effect/Thunk.scala
+++ /dev/null
@@ -1,29 +0,0 @@
-/*
- * Copyright 2020-2023 Typelevel
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package cats.effect
-
-/**
- * A utility to convert a by-name `thunk: => A` to a `Function0[A]` (its binary representation).
- * Scala 2 performs this optimization automatically but on Scala 3 the thunk is wrapped inside
- * of a new `Function0`. See https://github.com/typelevel/cats-effect/pull/2226
- */
-private object Thunk {
-  private[this] val impl =
-    ((x: Any) => x).asInstanceOf[(=> Any) => Function0[Any]]
-
-  def asFunction0[A](thunk: => A): Function0[A] = impl(thunk).asInstanceOf[Function0[A]]
-}
diff --git a/tests/shared/src/test/scala/cats/effect/ThunkSpec.scala b/tests/shared/src/test/scala/cats/effect/ThunkSpec.scala
index 92624ab5bd..f51f7b1e98 100644
--- a/tests/shared/src/test/scala/cats/effect/ThunkSpec.scala
+++ b/tests/shared/src/test/scala/cats/effect/ThunkSpec.scala
@@ -18,11 +18,11 @@ package cats.effect
 
 class ThunkSpec extends BaseSpec {
 
-  "Thunk.asFunction0" should {
+  "IO.delay" should {
     "return the same function" in {
       var i = 0
       val f = () => i += 1
-      Thunk.asFunction0(f()) eq f
+      IO.delay(f()).asInstanceOf[IO.Delay[Unit]].thunk eq f
     }
   }