diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/ShadowCopyActionTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/ShadowCopyActionTest.kt
new file mode 100644
index 000000000..53d7b5e00
--- /dev/null
+++ b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/ShadowCopyActionTest.kt
@@ -0,0 +1,140 @@
+package com.github.jengelman.gradle.plugins.shadow.tasks
+
+import assertk.assertFailure
+import assertk.assertThat
+import assertk.assertions.hasMessage
+import assertk.assertions.isEqualTo
+import assertk.assertions.isInstanceOf
+import assertk.assertions.isTrue
+import com.github.jengelman.gradle.plugins.shadow.internal.createZipOutputStream
+import com.github.jengelman.gradle.plugins.shadow.internal.useZip
+import com.github.jengelman.gradle.plugins.shadow.util.noOpDelegate
+import java.io.ByteArrayInputStream
+import java.io.File
+import java.io.InputStream
+import java.io.OutputStream
+import org.apache.tools.zip.UnixStat
+import org.apache.tools.zip.Zip64RequiredException
+import org.gradle.api.file.FilePermissions
+import org.gradle.api.file.RelativePath
+import org.gradle.api.internal.file.DefaultFilePermissions
+import org.gradle.api.internal.file.copy.CopyActionProcessingStream
+import org.gradle.api.internal.file.copy.FileCopyDetailsInternal
+import org.gradle.api.tasks.bundling.ZipEntryCompression
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.condition.DisabledOnOs
+import org.junit.jupiter.api.condition.OS
+import org.junit.jupiter.api.io.TempDir
+
+@Suppress("DEPRECATION")
+class ShadowCopyActionTest {
+  @TempDir lateinit var tempDir: File
+
+  @DisabledOnOs(OS.WINDOWS) // TODO: The output jar can't be deleted due to stream closing.
+  @Test
+  fun throwsZip64RequiredExceptionWhenEntriesExceedLimitWithoutZip64() {
+    val action = ShadowCopyAction()
+    val stream = CopyActionProcessingStream { streamAction ->
+      // Standard ZIP limit is 65535 entries.
+      for (i in 0..65535) {
+        streamAction.processFile(dummyDetails("file_$i.txt"))
+      }
+    }
+
+    assertFailure { action.execute(stream) }
+      .isInstanceOf<Zip64RequiredException>()
+      .hasMessage(
+        """
+        |archive contains more than 65535 entries.
+        |
+        |To build this archive, please enable the zip64 extension. e.g.
+        |```kts
+        |tasks.shadowJar {
+        |  isZip64 = true
+        |}
+        |```
+        |See: https://docs.gradle.org/current/dsl/org.gradle.api.tasks.bundling.Zip.html#org.gradle.api.tasks.bundling.Zip:zip64 for more details.
+        """
+          .trimMargin()
+      )
+  }
+
+  @Test
+  fun throwsZip64RequiredExceptionWhenNestedInCause() {
+    val action = ShadowCopyAction()
+    val stream = CopyActionProcessingStream { _ ->
+      throw RuntimeException("Wrapping exception", Zip64RequiredException("entry too big"))
+    }
+
+    assertFailure { action.execute(stream) }
+      .isInstanceOf<Zip64RequiredException>()
+      .hasMessage(
+        """
+        |entry too big
+        |
+        |To build this archive, please enable the zip64 extension. e.g.
+        |```kts
+        |tasks.shadowJar {
+        |  isZip64 = true
+        |}
+        |```
+        |See: https://docs.gradle.org/current/dsl/org.gradle.api.tasks.bundling.Zip.html#org.gradle.api.tasks.bundling.Zip:zip64 for more details.
+        """
+          .trimMargin()
+      )
+  }
+
+  @Test
+  fun succeedsWhenZip64IsEnabledWithManyEntries() {
+    val zipFile = tempDir.resolve("output.jar")
+    val action = ShadowCopyAction(zipFile = zipFile, isZip64 = true)
+    val stream = CopyActionProcessingStream { streamAction ->
+      for (i in 0..65535) {
+        streamAction.processFile(dummyDetails("file_$i.txt"))
+      }
+    }
+
+    val result = action.execute(stream)
+    assertThat(result.didWork).isTrue()
+    zipFile.useZip { assertThat(size()).isEqualTo(65536) }
+  }
+
+  private fun ShadowCopyAction(
+    zipFile: File = tempDir.resolve("output.jar"),
+    isZip64: Boolean = false,
+  ) =
+    ShadowCopyAction(
+      zipFile = zipFile,
+      zipOutStream =
+        zipFile.createZipOutputStream(
+          entryCompression = ZipEntryCompression.DEFLATED,
+          isZip64 = isZip64,
+          encoding = null,
+        ),
+      transformers = emptySet(),
+      relocators = emptySet(),
+      unusedClasses = emptySet(),
+      isPreserveFileTimestamps = true,
+      failOnDuplicateEntries = false,
+    )
+}
+
+private fun dummyDetails(path: String): FileCopyDetailsInternal =
+  object : FileCopyDetailsInternal by noOpDelegate() {
+    private val _relativePath = RelativePath.parse(true, path)
+
+    override fun isDirectory(): Boolean = false
+
+    override fun getPath(): String = _relativePath.pathString
+
+    override fun getRelativePath(): RelativePath = _relativePath
+
+    override fun open(): InputStream = ByteArrayInputStream(ByteArray(0))
+
+    override fun copyTo(target: OutputStream) = Unit
+
+    override fun getLastModified(): Long = 0L
+
+    override fun getPermissions(): FilePermissions =
+      DefaultFilePermissions(UnixStat.DEFAULT_FILE_PERM)
+  }