diff --git a/src/Runner.Worker/ActionManager.cs b/src/Runner.Worker/ActionManager.cs
index 6fe22e6fb..04112b533 100644
--- a/src/Runner.Worker/ActionManager.cs
+++ b/src/Runner.Worker/ActionManager.cs
@@ -1042,7 +1042,7 @@ namespace GitHub.Runner.Worker
                 if (actionDefinitionData.Execution.ExecutionType == ActionExecutionType.Container)
                 {
                     var containerAction = actionDefinitionData.Execution as ContainerActionExecutionData;
-                    if (containerAction.Image.EndsWith("Dockerfile") || containerAction.Image.EndsWith("dockerfile"))
+                    if (DockerUtil.IsDockerfile(containerAction.Image))
                     {
                         var dockerFileFullPath = Path.Combine(actionEntryDirectory, containerAction.Image);
                         executionContext.Debug($"Dockerfile for action: '{dockerFileFullPath}'.");
diff --git a/src/Runner.Worker/Container/DockerUtil.cs b/src/Runner.Worker/Container/DockerUtil.cs
index b1aa5c6c6..8eb922493 100644
--- a/src/Runner.Worker/Container/DockerUtil.cs
+++ b/src/Runner.Worker/Container/DockerUtil.cs
@@ -1,5 +1,6 @@
-using System;
+using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text.RegularExpressions;
 
 namespace GitHub.Runner.Worker.Container
@@ -65,6 +66,16 @@ namespace GitHub.Runner.Worker.Container
             return "";
         }
 
+        public static bool IsDockerfile(string image)
+        {
+            if (image.StartsWith("docker://", StringComparison.OrdinalIgnoreCase))
+            {
+                return false;
+            }
+            var imageWithoutPath = image.Split('/').Last();
+            return imageWithoutPath.StartsWith("Dockerfile.", StringComparison.OrdinalIgnoreCase) || imageWithoutPath.EndsWith("Dockerfile", StringComparison.OrdinalIgnoreCase);
+        }
+
         public static string CreateEscapedOption(string flag, string key)
         {
             if (String.IsNullOrEmpty(key))
diff --git a/src/Runner.Worker/Handlers/ContainerActionHandler.cs b/src/Runner.Worker/Handlers/ContainerActionHandler.cs
index c1d57de11..9d9d20f17 100644
--- a/src/Runner.Worker/Handlers/ContainerActionHandler.cs
+++ b/src/Runner.Worker/Handlers/ContainerActionHandler.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -56,7 +56,7 @@ namespace GitHub.Runner.Worker.Handlers
             {
                 Data.Image = Data.Image.Substring("docker://".Length);
             }
-            else if (Data.Image.EndsWith("Dockerfile") || Data.Image.EndsWith("dockerfile"))
+            else if (DockerUtil.IsDockerfile(Data.Image))
             {
                 // ensure docker file exist
                 dockerFile = Path.Combine(ActionDirectory, Data.Image);
diff --git a/src/Test/L0/Container/DockerUtilL0.cs b/src/Test/L0/Container/DockerUtilL0.cs
index 92d353198..a872f8de7 100644
--- a/src/Test/L0/Container/DockerUtilL0.cs
+++ b/src/Test/L0/Container/DockerUtilL0.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using GitHub.Runner.Worker.Container;
 using Xunit;
@@ -145,6 +145,49 @@ namespace GitHub.Runner.Common.Tests.Worker.Container
             Assert.Equal(expected, actual);
         }
 
+        [Theory]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        [InlineData("dockerhub/repo", false)]
+        [InlineData("debian:latest", false)]
+        [InlineData("something/dockerfileimage", false)]
+        [InlineData("ghcr.io/docker/dockerfile", true)] // should be false but might break the current workflows
+        [InlineData("Dockerfile", true)]
+        [InlineData("Dockerfile.", true)]
+        [InlineData(".Dockerfile", true)]
+        [InlineData(".Dockerfile.", false)]
+        [InlineData("dockerfile", true)]
+        [InlineData("dockerfile.", true)]
+        [InlineData(".dockerfile", true)]
+        [InlineData(".dockerfile.", false)]
+        [InlineData("Dockerfile.test", true)]
+        [InlineData("test.Dockerfile", true)]
+        [InlineData("docker/dockerfile:latest", false)]
+        [InlineData("/some/path/dockerfile:latest", false)]
+        [InlineData("dockerfile:latest", false)]
+        [InlineData("Dockerfile:latest", false)]
+        [InlineData("dockerfile-latest", false)]
+        [InlineData("Dockerfile-latest", false)]
+        [InlineData("dockerfile.latest", true)]
+        [InlineData("Dockerfile.latest", true)]
+        [InlineData("../dockerfile/dockerfileone", false)]
+        [InlineData("../Dockerfile/dockerfileone", false)]
+        [InlineData("../dockerfile.test", true)]
+        [InlineData("../Dockerfile.test", true)]
+        [InlineData("./dockerfile/image", false)]
+        [InlineData("./Dockerfile/image", false)]
+        [InlineData("example/Dockerfile.test", true)]
+        [InlineData("./example/Dockerfile.test", true)]
+        [InlineData("example/test.dockerfile", true)]
+        [InlineData("./example/test.dockerfile", true)]
+        [InlineData("docker://Dockerfile", false)]
+        [InlineData("docker://ubuntu:latest", false)]
+        public void IsDockerfile(string input, bool expected)
+        {
+            var actual = DockerUtil.IsDockerfile(input);
+            Assert.Equal(expected, actual);
+        }
+
         [Theory]
         [Trait("Level", "L0")]
         [Trait("Category", "Worker")]