diff --git a/bake/compose.go b/bake/compose.go
index 44bfe5dc..37e7782e 100644
--- a/bake/compose.go
+++ b/bake/compose.go
@@ -187,25 +187,25 @@ func (t *Target) composeExtTarget(exts map[string]interface{}) error {
 	}
 
 	if len(xb.Tags) > 0 {
-		t.Tags = append(t.Tags, xb.Tags...)
+		t.Tags = dedupString(append(t.Tags, xb.Tags...))
 	}
 	if len(xb.CacheFrom) > 0 {
-		t.CacheFrom = append(t.CacheFrom, xb.CacheFrom...)
+		t.CacheFrom = dedupString(append(t.CacheFrom, xb.CacheFrom...))
 	}
 	if len(xb.CacheTo) > 0 {
-		t.CacheTo = append(t.CacheTo, xb.CacheTo...)
+		t.CacheTo = dedupString(append(t.CacheTo, xb.CacheTo...))
 	}
 	if len(xb.Secrets) > 0 {
-		t.Secrets = append(t.Secrets, xb.Secrets...)
+		t.Secrets = dedupString(append(t.Secrets, xb.Secrets...))
 	}
 	if len(xb.SSH) > 0 {
-		t.SSH = append(t.SSH, xb.SSH...)
+		t.SSH = dedupString(append(t.SSH, xb.SSH...))
 	}
 	if len(xb.Platforms) > 0 {
-		t.Platforms = append(t.Platforms, xb.Platforms...)
+		t.Platforms = dedupString(append(t.Platforms, xb.Platforms...))
 	}
 	if len(xb.Outputs) > 0 {
-		t.Outputs = append(t.Outputs, xb.Outputs...)
+		t.Outputs = dedupString(append(t.Outputs, xb.Outputs...))
 	}
 	if xb.Pull != nil {
 		t.Pull = xb.Pull
@@ -214,7 +214,7 @@ func (t *Target) composeExtTarget(exts map[string]interface{}) error {
 		t.NoCache = xb.NoCache
 	}
 	if len(xb.NoCacheFilter) > 0 {
-		t.NoCacheFilter = append(t.NoCacheFilter, xb.NoCacheFilter...)
+		t.NoCacheFilter = dedupString(append(t.NoCacheFilter, xb.NoCacheFilter...))
 	}
 
 	return nil
diff --git a/bake/compose_test.go b/bake/compose_test.go
index 7ab3ad9f..a3af03b9 100644
--- a/bake/compose_test.go
+++ b/bake/compose_test.go
@@ -316,6 +316,37 @@ services:
 	require.Equal(t, c.Targets[1].NoCache, newBool(true))
 }
 
+func TestComposeExtDedup(t *testing.T) {
+	var dt = []byte(`
+services:
+  webapp:
+    image: app:bar
+    build:
+      cache_from:
+        - user/app:cache
+      cache_to:
+        - user/app:cache
+      tags:
+        - ct-addon:foo
+      x-bake:
+        tags:
+          - ct-addon:foo
+          - ct-addon:baz
+        cache-from:
+          - user/app:cache
+          - type=local,src=path/to/cache
+        cache-to:
+          - type=local,dest=path/to/cache
+`)
+
+	c, err := ParseCompose(dt)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(c.Targets))
+	require.Equal(t, c.Targets[0].Tags, []string{"ct-addon:foo", "ct-addon:baz"})
+	require.Equal(t, c.Targets[0].CacheFrom, []string{"user/app:cache", "type=local,src=path/to/cache"})
+	require.Equal(t, c.Targets[0].CacheTo, []string{"user/app:cache", "type=local,dest=path/to/cache"})
+}
+
 func TestEnv(t *testing.T) {
 	envf, err := os.CreateTemp("", "env")
 	require.NoError(t, err)