diff --git a/core/src/main/java/google/registry/flows/domain/DomainFlowUtils.java b/core/src/main/java/google/registry/flows/domain/DomainFlowUtils.java
index d72bce3c6..f92b4d372 100644
--- a/core/src/main/java/google/registry/flows/domain/DomainFlowUtils.java
+++ b/core/src/main/java/google/registry/flows/domain/DomainFlowUtils.java
@@ -1397,7 +1397,7 @@ public class DomainFlowUtils {
   }
 
   /** Domain name is under tld which doesn't exist. */
-  static class TldDoesNotExistException extends ParameterValueRangeErrorException {
+  public static class TldDoesNotExistException extends ParameterValueRangeErrorException {
     public TldDoesNotExistException(String tld) {
       super(String.format("Domain name is under tld %s which doesn't exist", tld));
     }
diff --git a/core/src/main/java/google/registry/rdap/RdapDataStructures.java b/core/src/main/java/google/registry/rdap/RdapDataStructures.java
index 6bb2a3410..fe8ca9bb5 100644
--- a/core/src/main/java/google/registry/rdap/RdapDataStructures.java
+++ b/core/src/main/java/google/registry/rdap/RdapDataStructures.java
@@ -333,7 +333,6 @@ final class RdapDataStructures {
    */
   @RestrictJsonNames("status[]")
   enum RdapStatus implements Jsonable {
-
     // Status values specified in RFC 9083 § 10.2.2.
     VALIDATED("validated"),
     RENEW_PROHIBITED("renew prohibited"),
diff --git a/core/src/main/java/google/registry/rdap/RdapDomainAction.java b/core/src/main/java/google/registry/rdap/RdapDomainAction.java
index 6b96b3ec2..a20b5b625 100644
--- a/core/src/main/java/google/registry/rdap/RdapDomainAction.java
+++ b/core/src/main/java/google/registry/rdap/RdapDomainAction.java
@@ -57,6 +57,9 @@ public class RdapDomainAction extends RdapActionBase {
     InternetDomainName domainName;
     try {
       domainName = validateDomainName(pathSearchString);
+    } catch (DomainFlowUtils.TldDoesNotExistException e) {
+      // A special case where a valid domain name on a nonexistent TLD should return 404
+      throw new NotFoundException(pathSearchString + " not found");
     } catch (EppException e) {
       throw new BadRequestException(
           String.format(
diff --git a/core/src/test/java/google/registry/rdap/RdapDomainActionTest.java b/core/src/test/java/google/registry/rdap/RdapDomainActionTest.java
index 2d84042cf..d3e5523d4 100644
--- a/core/src/test/java/google/registry/rdap/RdapDomainActionTest.java
+++ b/core/src/test/java/google/registry/rdap/RdapDomainActionTest.java
@@ -57,12 +57,7 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
-/**
- * Unit tests for {@link RdapDomainAction}.
- *
- * <p>TODO(b/26872828): The next time we do any work on RDAP, consider adding the APNIC RDAP
- * conformance checker to the unit test suite.
- */
+/** Unit tests for {@link RdapDomainAction}. */
 class RdapDomainActionTest extends RdapActionBaseTestCase<RdapDomainAction> {
 
   RdapDomainActionTest() {
@@ -260,15 +255,11 @@ class RdapDomainActionTest extends RdapActionBaseTestCase<RdapDomainAction> {
   }
 
   @Test
-  void testUnknownDomain_returns400() {
+  void testUnknownDomain_returns404() {
     assertAboutJson()
         .that(generateActualJson("missingdomain.com"))
-        .isEqualTo(
-            generateExpectedJsonError(
-                "missingdomain.com is not a valid domain name: Domain name is under tld com which"
-                    + " doesn't exist",
-                400));
-    assertThat(response.getStatus()).isEqualTo(400);
+        .isEqualTo(generateExpectedJsonError("missingdomain.com not found", 404));
+    assertThat(response.getStatus()).isEqualTo(404);
   }
 
   @Test