diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -284,7 +284,11 @@
   }
   const username = request.username ?? request.usernameOrEmail;
   if (!username) {
-    throw new ServerError('invalid_parameters');
+    if (hasMinCodeVersion(viewer.platformDetails, 150)) {
+      throw new ServerError('invalid_credentials');
+    } else {
+      throw new ServerError('invalid_parameters');
+    }
   }
   const userQuery = SQL`
     SELECT id, hash, username
@@ -297,16 +301,19 @@
   } = await promiseAll(promises);
 
   if (userResult.length === 0) {
-    throw new ServerError('invalid_parameters');
+    if (hasMinCodeVersion(viewer.platformDetails, 150)) {
+      throw new ServerError('invalid_credentials');
+    } else {
+      throw new ServerError('invalid_parameters');
+    }
   }
+
   const userRow = userResult[0];
+
   if (!userRow.hash || !bcrypt.compareSync(request.password, userRow.hash)) {
-    if (hasMinCodeVersion(viewer.platformDetails, 99999)) {
-      throw new ServerError('invalid_parameters');
-    } else {
-      throw new ServerError('invalid_credentials');
-    }
+    throw new ServerError('invalid_credentials');
   }
+
   const id = userRow.id.toString();
   return await processSuccessfulLogin(viewer, input, id, calendarQuery);
 }
diff --git a/keyserver/src/utils/validation-utils.js b/keyserver/src/utils/validation-utils.js
--- a/keyserver/src/utils/validation-utils.js
+++ b/keyserver/src/utils/validation-utils.js
@@ -18,14 +18,19 @@
   if (!viewer.isSocket) {
     await checkClientSupported(viewer, inputValidator, input);
   }
-  checkInputValidator(inputValidator, input);
+  checkInputValidator(viewer, inputValidator, input);
 }
 
-function checkInputValidator(inputValidator: *, input: *) {
+function checkInputValidator(inputValidator: *, input: *, viewer?: Viewer) {
   if (!inputValidator || inputValidator.is(input)) {
     return;
   }
-  const error = new ServerError('invalid_parameters');
+  let error;
+  if (viewer && hasMinCodeVersion(viewer.platformDetails, 150)) {
+    error = new ServerError('invalid_credentials');
+  } else {
+    error = new ServerError('invalid_parameters');
+  }
   error.sanitizedInput = input ? sanitizeInput(inputValidator, input) : null;
   throw error;
 }