diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8ec98f16..3a6c78d7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,11 @@
 
 - update all extensions to use multi-error for gathering validation errors.
 
+Breaking changes
+
+- `bnsd/x/username`: `iov` is the only valid and accepted domain name for a
+  username. This limitation is forced for the MVP release as we do not have
+  namespace management implemented.
 
 ## 0.19.0
 
diff --git a/cmd/bnsd/x/username/username.go b/cmd/bnsd/x/username/username.go
index d67443f8..b007507e 100644
--- a/cmd/bnsd/x/username/username.go
+++ b/cmd/bnsd/x/username/username.go
@@ -52,6 +52,15 @@ func (u Username) Validate() error {
 	if !validUsername(string(u)) {
 		return errors.Wrap(errors.ErrInput, "invalid username")
 	}
+
+	// Currently only IOV namespace is supported. This is a public
+	// namespace that anyone can register in an IOV owns. This limitation
+	// exists because for the MVP release we do not provide a way to
+	// register and manage namespaces.
+	if u.Domain() != "iov" {
+		return errors.Field("Domain", errors.ErrInput, "invalid namespace")
+	}
+
 	return nil
 }
 
diff --git a/cmd/bnsd/x/username/username_test.go b/cmd/bnsd/x/username/username_test.go
index 6ef5f52a..f99c4c21 100644
--- a/cmd/bnsd/x/username/username_test.go
+++ b/cmd/bnsd/x/username/username_test.go
@@ -20,14 +20,14 @@ func TestUsername(t *testing.T) {
 			WantDomain: "iov",
 		},
 		"shortest valid name and domain": {
-			Raw:        strings.Repeat("x", 4) + "*" + strings.Repeat("x", 3),
+			Raw:        strings.Repeat("x", 4) + "*iov",
 			WantName:   strings.Repeat("x", 4),
-			WantDomain: strings.Repeat("x", 3),
+			WantDomain: "iov",
 		},
 		"longest valid name and domain": {
-			Raw:        strings.Repeat("x", 64) + "*" + strings.Repeat("x", 16),
+			Raw:        strings.Repeat("x", 64) + "*iov",
 			WantName:   strings.Repeat("x", 64),
-			WantDomain: strings.Repeat("x", 16),
+			WantDomain: "iov",
 		},
 		"too long name": {
 			Raw:        strings.Repeat("x", 65) + "*" + strings.Repeat("x", 6),
@@ -60,10 +60,10 @@ func TestUsername(t *testing.T) {
 			WantDomain: "",
 		},
 		"missing name": {
-			Raw:        "*foo",
+			Raw:        "*iov",
 			WantErr:    errors.ErrInput,
 			WantName:   "",
-			WantDomain: "foo",
+			WantDomain: "iov",
 		},
 		"missing separator": {
 			Raw:        "xyz",
@@ -77,6 +77,12 @@ func TestUsername(t *testing.T) {
 			WantName:   "😈",
 			WantDomain: "😀",
 		},
+		"invalid domain name": {
+			Raw:        "extreme*expert",
+			WantErr:    errors.ErrInput,
+			WantName:   "extreme",
+			WantDomain: "expert",
+		},
 	}
 
 	for testName, tc := range cases {