diff --git a/detect.go b/detect.go
index e4b3066..58f0360 100644
--- a/detect.go
+++ b/detect.go
@@ -15,7 +15,16 @@ func Detect() packit.DetectFunc {
 			if os.IsNotExist(err) {
 				return packit.DetectResult{}, packit.Fail
 			}
-			return packit.DetectResult{}, fmt.Errorf("Failed to stat Gopkg.toml : %w", err)
+			return packit.DetectResult{}, fmt.Errorf("failed to stat Gopkg.toml: %w", err)
+		}
+
+		_, err = os.Stat(filepath.Join(context.WorkingDir, "vendor"))
+		if err == nil {
+			return packit.DetectResult{}, packit.Fail
+		} else {
+			if !os.IsNotExist(err) {
+				return packit.DetectResult{}, fmt.Errorf("failed to stat vendor directory: %w", err)
+			}
 		}
 
 		return packit.DetectResult{
diff --git a/detect_test.go b/detect_test.go
index 9a4fc03..3b80444 100644
--- a/detect_test.go
+++ b/detect_test.go
@@ -65,4 +65,36 @@ func testDetect(t *testing.T, context spec.G, it spec.S) {
 			Expect(err).To(MatchError(packit.Fail))
 		})
 	})
+
+	context("when there is a vendor directory in the working directory", func() {
+		it.Before(func() {
+			Expect(os.MkdirAll(filepath.Join(workingDir, "vendor"), os.ModePerm)).To(Succeed())
+		})
+
+		it("fails detection", func() {
+			_, err := detect(packit.DetectContext{
+				WorkingDir: workingDir,
+			})
+			Expect(err).To(MatchError(packit.Fail))
+		})
+	})
+
+	context("failure cases", func() {
+		context("the workspace directory cannot be accessed", func() {
+			it.Before(func() {
+				Expect(os.Chmod(workingDir, 0000)).To(Succeed())
+			})
+
+			it.After(func() {
+				Expect(os.Chmod(workingDir, os.ModePerm)).To(Succeed())
+			})
+
+			it("returns an error", func() {
+				_, err := detect(packit.DetectContext{
+					WorkingDir: workingDir,
+				})
+				Expect(err).To(MatchError(ContainSubstring("failed to stat Gopkg.toml:")))
+			})
+		})
+	})
 }