diff --git a/py-image-builder/e2e/e2e_test.go b/py-image-builder/e2e/e2e_test.go
index c045d5d..68e48e6 100644
--- a/py-image-builder/e2e/e2e_test.go
+++ b/py-image-builder/e2e/e2e_test.go
@@ -307,7 +307,7 @@ func pythonTag(t *testing.T, py string) string {
 func extract(t *testing.T, img v1.Image, dest string) {
 	t.Helper()
 	rc := mutate.Extract(img)
-	defer rc.Close()
+	defer func() { _ = rc.Close() }()
 	tr := tar.NewReader(rc)
 	for {
 		h, err := tr.Next()
@@ -332,10 +332,10 @@ func extract(t *testing.T, img v1.Image, dest string) {
 				t.Fatal(err)
 			}
 			if _, err := io.Copy(f, tr); err != nil {
-				f.Close()
+				_ = f.Close()
 				t.Fatal(err)
 			}
-			f.Close()
+			_ = f.Close()
 		}
 	}
 }
diff --git a/py-image-builder/internal/build/build.go b/py-image-builder/internal/build/build.go
index 3fdc9cb..17b4d52 100644
--- a/py-image-builder/internal/build/build.go
+++ b/py-image-builder/internal/build/build.go
@@ -161,7 +161,7 @@ func wheelFiles(rw wheelhouse.ResolvedWheel, layout wheel.Layout) ([]ptar.File,
 	if err != nil {
 		return nil, err
 	}
-	defer w.Close()
+	defer func() { _ = w.Close() }()
 	return w.Files(layout)
 }
 
diff --git a/py-image-builder/internal/build/build_test.go b/py-image-builder/internal/build/build_test.go
index 30ef1be..2a2005b 100644
--- a/py-image-builder/internal/build/build_test.go
+++ b/py-image-builder/internal/build/build_test.go
@@ -22,7 +22,7 @@ func layerPaths(t *testing.T, l v1.Layer) map[string]bool {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer rc.Close()
+	defer func() { _ = rc.Close() }()
 	names := map[string]bool{}
 	tr := tar.NewReader(rc)
 	for {
@@ -140,7 +140,7 @@ func TestConfigAndLayerCount(t *testing.T) {
 	if c.Labels["org.test"] != "yes" {
 		t.Errorf("label not set: %v", c.Labels)
 	}
-	if !cf.Created.Time.Equal(epoch()) {
+	if !cf.Created.Equal(epoch()) {
 		t.Errorf("config Created = %v, want epoch", cf.Created)
 	}
 }
diff --git a/py-image-builder/internal/lock/lock.go b/py-image-builder/internal/lock/lock.go
index a2eb194..9d27648 100644
--- a/py-image-builder/internal/lock/lock.go
+++ b/py-image-builder/internal/lock/lock.go
@@ -46,7 +46,7 @@ func ParseFile(path string) ([]Requirement, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 	return Parse(f)
 }
 
diff --git a/py-image-builder/internal/wheel/wheel.go b/py-image-builder/internal/wheel/wheel.go
index ab1cd1e..4b990fe 100644
--- a/py-image-builder/internal/wheel/wheel.go
+++ b/py-image-builder/internal/wheel/wheel.go
@@ -88,7 +88,7 @@ func Open(filename string) (*Wheel, error) {
 		}
 	}
 	if w.distInfo == "" {
-		z.Close()
+		_ = z.Close()
 		return nil, fmt.Errorf("wheel: %q has no .dist-info directory", filename)
 	}
 	base := strings.TrimSuffix(w.distInfo, ".dist-info")
@@ -250,7 +250,7 @@ func readZip(f *zip.File) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer rc.Close()
+	defer func() { _ = rc.Close() }()
 	return io.ReadAll(rc)
 }
 
diff --git a/py-image-builder/internal/wheel/wheel_test.go b/py-image-builder/internal/wheel/wheel_test.go
index e273e6f..55beab5 100644
--- a/py-image-builder/internal/wheel/wheel_test.go
+++ b/py-image-builder/internal/wheel/wheel_test.go
@@ -43,7 +43,7 @@ func TestFilesLayout(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer w.Close()
+	defer func() { _ = w.Close() }()
 
 	if w.Name != "examplepkg" || w.Version != "1.2.3" {
 		t.Fatalf("parsed name/version = %q %q", w.Name, w.Version)
@@ -92,7 +92,7 @@ func TestFilesDeterministic(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		defer w.Close()
+		defer func() { _ = w.Close() }()
 		files, err := w.Files(layout)
 		if err != nil {
 			t.Fatal(err)
@@ -107,7 +107,8 @@ func TestFilesDeterministic(t *testing.T) {
 		}
 		return d.String()
 	}
-	if digest() != digest() {
-		t.Fatal("wheel layer digest is not deterministic")
+	d1, d2 := digest(), digest()
+	if d1 != d2 {
+		t.Fatalf("wheel layer digest is not deterministic: %s != %s", d1, d2)
 	}
 }