diff --git a/changelog.d/2451.bugfix.2.md b/changelog.d/2451.bugfix.2.md
new file mode 100644
index 000000000..49cf46a52
--- /dev/null
+++ b/changelog.d/2451.bugfix.2.md
@@ -0,0 +1 @@
+Setting profile data that would make the profile exceed 64 KiB now returns 400 `M_PROFILE_TOO_LARGE` as required by the spec, instead of a 500 error.
diff --git a/src/service/users/profile.rs b/src/service/users/profile.rs
index b2c0c3e3b..cad67765c 100644
--- a/src/service/users/profile.rs
+++ b/src/service/users/profile.rs
@@ -80,10 +80,10 @@ impl super::Service {
 					.len()
 					> MAX_PROFILE_LENGTH_BYTES
 				{
-					return Err!(
+					return Err!(Request(ProfileTooLarge(
 						"Profile data must not exceed {MAX_PROFILE_LENGTH_BYTES} bytes in \
 						 length."
-					);
+					)));
 				}
 			} else {
 				return Err!(Request(BadJson("Failed to canonicalize profile.")));