diff --git a/docs/proposal/203-duffle-build.md b/docs/proposal/203-duffle-build.md
index f06bdb89..780aab91 100644
--- a/docs/proposal/203-duffle-build.md
+++ b/docs/proposal/203-duffle-build.md
@@ -1,5 +1,5 @@
 # Duffle Build
 
-This document describes how `duffle build` works, and how it uses the duffle build file: `duffle.json, duffle.yaml, duffle.toml`.
+This document describes how `duffle build` works, and how it uses the duffle build file: `duffle.json`.
 
-`duffle build` take a path to a directory that contains a duffle build file (`duffle.json, duffle.toml, or duffle.yaml`) to build a Cloud Native Application Bundle (CNAB). In the process, it also builds all of the invocation images specified in the duffle build file.
+`duffle build` take a path to a directory that contains a duffle build file (`duffle.json`) to build a Cloud Native Application Bundle (CNAB). In the process, it also builds all of the invocation images specified in the duffle build file.
diff --git a/pkg/duffle/manifest/manifest_test.go b/pkg/duffle/manifest/manifest_test.go
index 646a8b24..78dede9d 100644
--- a/pkg/duffle/manifest/manifest_test.go
+++ b/pkg/duffle/manifest/manifest_test.go
@@ -28,7 +28,7 @@ func TestGenerateName(t *testing.T) {
 }
 
 func TestLoad(t *testing.T) {
-	testcases := []string{"", "duffle.toml", "duffle.json", "duffle.yaml"}
+	testcases := []string{"", "duffle.json"}
 
 	for _, tc := range testcases {
 		t.Run(tc, func(t *testing.T) {
diff --git a/pkg/duffle/manifest/testdata/duffle.toml b/pkg/duffle/manifest/testdata/duffle.toml
deleted file mode 100644
index f380b2f1..00000000
--- a/pkg/duffle/manifest/testdata/duffle.toml
+++ /dev/null
@@ -1,21 +0,0 @@
-name = "testbundle"
-[invocationImages]
-    [invocationImages.cnab]
-        name = "cnab"
-        builder = "docker"
-        configuration = { registry = "microsoft" }
-[images]
-[images.istio]
-    description = "istio images"
-    imageType = "docker"
-    image = "docker.io/istio/citadel:1.0.2"
-    digest = "sha256:ca4050c9fed3a2ddcaef32140686613c4110ed728f53262d0a23a7e17da73111"
-[definitions.foo]
-    type = "string"
-[parameters.fields.foo]
-    definition = "foo"
-[credentials.bar]
-    path = "/tmp"
-
-[[maintainers]]
-  name = "sally"
diff --git a/pkg/duffle/manifest/testdata/duffle.yaml b/pkg/duffle/manifest/testdata/duffle.yaml
deleted file mode 100644
index e19f7779..00000000
--- a/pkg/duffle/manifest/testdata/duffle.yaml
+++ /dev/null
@@ -1,26 +0,0 @@
-name: testbundle
-invocationImages:
-  cnab:
-    name: cnab
-    builder: docker
-    configuration:
-      registry: microsoft
-images:
-  istio:
-    description: "istio images"
-    imageType: "docker"
-    image: "docker.io/istio/citadel:1.0.2"
-    digest: "sha256:ca4050c9fed3a2ddcaef32140686613c4110ed728f53262d0a23a7e17da73111"
-definitions:
-  foo:
-    type: string
-parameters:
-  Fields:
-    foo:
-      definition: foo
-credentials:
-  bar:
-    path: /tmp
-maintainers:
-- name: sally
-