diff --git a/pkg/sif/image.go b/pkg/sif/image.go
index 3835ac3..bee9068 100644
--- a/pkg/sif/image.go
+++ b/pkg/sif/image.go
@@ -28,15 +28,18 @@ var (
 	errMultipleMatchingImages = errors.New("multiple images match criteria")
 )
 
-// Image returns a single Image stored in f, that is selected by the provided
-// Matcher. If more than one image matches, or no image matches, an error is
-// returned.
+// Image returns a single Image stored in f, that is selected by m. If m is nil, all manifests are
+// selected. If more than one image matches, or no image matches, an error is returned.
 func (f *OCIFileImage) Image(m match.Matcher, _ ...Option) (v1.Image, error) {
 	ri, err := f.RootIndex()
 	if err != nil {
 		return nil, err
 	}
 
+	if m == nil {
+		m = matchAll
+	}
+
 	matches, err := partial.FindImages(ri, m)
 	if err != nil {
 		return nil, err
diff --git a/pkg/sif/image_test.go b/pkg/sif/image_test.go
index c274570..433e6b8 100644
--- a/pkg/sif/image_test.go
+++ b/pkg/sif/image_test.go
@@ -106,6 +106,12 @@ func Test_OCIFileImage_Image(t *testing.T) {
 			wantImage: nil,
 			wantErr:   true,
 		},
+		{
+			name:      "NilMatcher",
+			matcher:   nil,
+			wantImage: nil,
+			wantErr:   true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
diff --git a/pkg/sif/index.go b/pkg/sif/index.go
index ee17ae2..480c177 100644
--- a/pkg/sif/index.go
+++ b/pkg/sif/index.go
@@ -72,15 +72,18 @@ var (
 	errMultipleMatchingIndices = errors.New("multiple indices match criteria")
 )
 
-// Index returns a single ImageIndex stored in f, that is selected by the provided
-// Matcher. If more than one index matches, or no index matches, an error is
-// returned.
+// Index returns a single ImageIndex stored in f, that is selected by m. If m is nil, all manifests
+// are selected. If more than one index matches, or no image matches, an error is returned.
 func (f *OCIFileImage) Index(m match.Matcher, _ ...Option) (v1.ImageIndex, error) {
 	ri, err := f.RootIndex()
 	if err != nil {
 		return nil, err
 	}
 
+	if m == nil {
+		m = matchAll
+	}
+
 	matches, err := partial.FindIndexes(ri, m)
 	if err != nil {
 		return nil, err
diff --git a/pkg/sif/index_test.go b/pkg/sif/index_test.go
index 53afe5e..fa08116 100644
--- a/pkg/sif/index_test.go
+++ b/pkg/sif/index_test.go
@@ -163,6 +163,12 @@ func Test_OCIFileImage_Index(t *testing.T) {
 			wantIndex: nil,
 			wantErr:   true,
 		},
+		{
+			name:      "NilMatcher",
+			matcher:   nil,
+			wantIndex: nil,
+			wantErr:   true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
diff --git a/pkg/sif/match.go b/pkg/sif/match.go
new file mode 100644
index 0000000..38eaa91
--- /dev/null
+++ b/pkg/sif/match.go
@@ -0,0 +1,9 @@
+// Copyright 2024 Sylabs Inc. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sif
+
+import v1 "github.com/google/go-containerregistry/pkg/v1"
+
+func matchAll(v1.Descriptor) bool { return true }
diff --git a/pkg/sif/testdata/TestRemoveManifests/NilMatcher.golden b/pkg/sif/testdata/TestRemoveManifests/NilMatcher.golden
new file mode 100644
index 0000000..dc375f5
Binary files /dev/null and b/pkg/sif/testdata/TestRemoveManifests/NilMatcher.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceImageNilMatcher.golden b/pkg/sif/testdata/TestReplace/ReplaceImageNilMatcher.golden
new file mode 100644
index 0000000..a650261
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceImageNilMatcher.golden differ
diff --git a/pkg/sif/testdata/TestReplace/ReplaceIndexNilMatcher.golden b/pkg/sif/testdata/TestReplace/ReplaceIndexNilMatcher.golden
new file mode 100644
index 0000000..cdec4e3
Binary files /dev/null and b/pkg/sif/testdata/TestReplace/ReplaceIndexNilMatcher.golden differ
diff --git a/pkg/sif/update.go b/pkg/sif/update.go
index 20fa460..d51301b 100644
--- a/pkg/sif/update.go
+++ b/pkg/sif/update.go
@@ -461,31 +461,40 @@ func (f *OCIFileImage) RemoveBlob(hash v1.Hash) error {
 		sif.OptDeleteCompact(true))
 }
 
-// RemoveManifests modifies the SIF file associated with f so that its RootIndex
-// no longer holds manifests selected by matcher. Any blobs in the SIF that are
-// no longer referenced are removed from the SIF.
+// RemoveManifests modifies the SIF file associated with f so that its
+// RootIndex no longer holds manifests selected by matcher. If m is nil, all
+// manifests are selected. Any blobs in the SIF that are no longer referenced
+// are removed from the SIF.
 func (f *OCIFileImage) RemoveManifests(matcher match.Matcher) error {
 	ri, err := f.RootIndex()
 	if err != nil {
 		return err
 	}
+
+	if matcher == nil {
+		matcher = matchAll
+	}
+
 	return f.UpdateRootIndex(mutate.RemoveManifests(ri, matcher))
 }
 
 // ReplaceImage writes img to the SIF, replacing any existing manifest that is
-// selected by the matcher. Any blobs in the SIF that are no longer referenced
-// are removed from the SIF.
+// selected by the matcher. If m is nil, all manifests are selected. Any blobs
+// in the SIF that are no longer referenced are removed from the SIF.
 func (f *OCIFileImage) ReplaceImage(img v1.Image, matcher match.Matcher, opts ...AppendOpt) error {
 	return f.replace(img, matcher, opts...)
 }
 
 // ReplaceIndex writes ii to the SIF, replacing any existing manifest that is
-// selected by the matcher. Any blobs in the SIF that are no longer referenced
-// are removed from the SIF.
+// selected by the matcher. If m is nil, all manifests are selected. Any blobs
+// in the SIF that are no longer referenced are removed from the SIF.
 func (f *OCIFileImage) ReplaceIndex(ii v1.ImageIndex, matcher match.Matcher, opts ...AppendOpt) error {
 	return f.replace(ii, matcher, opts...)
 }
 
+// replace writes add to the SIF, replacing any existing manifest that is
+// selected by the matcher. If m is nil, all manifests are selected. Any blobs
+// in the SIF that are no longer referenced are removed from the SIF.
 func (f *OCIFileImage) replace(add mutate.Appendable, matcher match.Matcher, opts ...AppendOpt) error {
 	ao := appendOpts{
 		tempDir: os.TempDir(),
@@ -496,6 +505,10 @@ func (f *OCIFileImage) replace(add mutate.Appendable, matcher match.Matcher, opt
 		}
 	}
 
+	if matcher == nil {
+		matcher = matchAll
+	}
+
 	ri, err := f.RootIndex()
 	if err != nil {
 		return err
diff --git a/pkg/sif/update_test.go b/pkg/sif/update_test.go
index 2cb1ca0..7000e43 100644
--- a/pkg/sif/update_test.go
+++ b/pkg/sif/update_test.go
@@ -404,6 +404,11 @@ func TestRemoveManifests(t *testing.T) {
 			base:    "hello-world-docker-v2-manifest-list",
 			matcher: match.Platforms(v1.Platform{OS: "linux", Architecture: "m68k"}),
 		},
+		{
+			name:    "NilMatcher",
+			base:    "hello-world-docker-v2-manifest-list",
+			matcher: nil,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -478,6 +483,12 @@ func TestReplace(t *testing.T) {
 			replacement: replaceImage,
 			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "m68k"}),
 		},
+		{
+			name:        "ReplaceImageNilMatcher",
+			base:        "hello-world-docker-v2-manifest",
+			replacement: replaceImage,
+			matcher:     nil,
+		},
 		{
 			name:        "ReplaceIndexManifest",
 			base:        "hello-world-docker-v2-manifest",
@@ -496,6 +507,12 @@ func TestReplace(t *testing.T) {
 			replacement: replaceIndex,
 			matcher:     match.Platforms(v1.Platform{OS: "linux", Architecture: "m68k"}),
 		},
+		{
+			name:        "ReplaceIndexNilMatcher",
+			base:        "hello-world-docker-v2-manifest",
+			replacement: replaceIndex,
+			matcher:     nil,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {