diff --git a/cassandane/Cassandane/Cyrus/JMAPCore.pm b/cassandane/Cassandane/Cyrus/JMAPCore.pm
index 176010d7cd..ea69efb7b2 100644
--- a/cassandane/Cassandane/Cyrus/JMAPCore.pm
+++ b/cassandane/Cassandane/Cyrus/JMAPCore.pm
@@ -66,6 +66,7 @@ sub new
     $config->set(caldav_realm => 'Cassandane',
                  conversations => 'yes',
                  httpmodules => 'carddav caldav jmap',
+                 jmap_max_size_upload => '1k',
                  httpallowcompress => 'no');
 
     return $class->SUPER::new({
@@ -998,4 +999,54 @@ sub test_get_session_rename_race
     $self->assert_not_null($RawResponse->{headers}{'retry-after'});
 }
 
+sub test_blob_upload_too_large
+    :min_version_3_9 :needs_component_jmap :JMAPExtensions
+{
+    my $self = shift;
+    my $jmap = $self->{jmap};
+
+    xlog "Assert Problem Details report";
+    my $httpReq = {
+        headers => {
+            'Authorization' => $jmap->auth_header(),
+        },
+        content => 'X' x 1025,
+    };
+    my $httpRes = $jmap->ua->post($jmap->uploaduri('cassandane'), $httpReq);
+    if ($ENV{DEBUGJMAP}) {
+        warn "JMAP " . Dumper($httpReq, $httpRes);
+    }
+    $self->assert_str_equals("413", $httpRes->{status});
+    my $res = eval { decode_json($httpRes->{content}) };
+    $self->assert_str_equals("413", $res->{status});
+    $self->assert_str_equals("Content Too Large", $res->{title});
+    $self->assert_str_equals("urn:ietf:params:jmap:error:limit", $res->{type});
+    $self->assert_str_equals("maxSizeUpload", $res->{limit});
+}
+
+sub test_blob_upload_bad_url
+    :min_version_3_9 :needs_component_jmap :JMAPExtensions
+{
+    my $self = shift;
+    my $jmap = $self->{jmap};
+
+    xlog "Assert Problem Details report";
+    my $httpReq = {
+        headers => {
+            'Authorization' => $jmap->auth_header(),
+        },
+        content => 'Hello World',
+    };
+    my $httpRes = $jmap->ua->post($jmap->uploaduri('cassandane') . 'X', $httpReq);
+    if ($ENV{DEBUGJMAP}) {
+        warn "JMAP " . Dumper($httpReq, $httpRes);
+    }
+    $self->assert_str_equals("404", $httpRes->{status});
+    my $res = eval { decode_json($httpRes->{content}) };
+    $self->assert_str_equals("404", $res->{status});
+    $self->assert_str_equals("Not Found", $res->{title});
+    $self->assert_str_equals("about:blank", $res->{type});
+    $self->assert_str_equals("unknown uploadUrl", $res->{detail});
+}
+
 1;
diff --git a/imap/http_jmap.c b/imap/http_jmap.c
index 09c18fc424..cbd257ac8b 100644
--- a/imap/http_jmap.c
+++ b/imap/http_jmap.c
@@ -1022,6 +1022,7 @@ static int jmap_upload(struct transaction_t *txn)
     const char **hdr;
     time_t now = time(NULL);
     struct appendstate as;
+    char *accountid = NULL;
     char *normalisedtype = NULL;
     int rawmessage = 0;
     struct conversations_state *cstate = NULL;
@@ -1041,14 +1042,16 @@ static int jmap_upload(struct transaction_t *txn)
 
     if (datalen > (size_t) my_jmap_settings.limits[MAX_SIZE_UPLOAD]) {
         txn->error.desc = "JSON upload byte size exceeds maxSizeUpload";
-        return HTTP_CONTENT_TOO_LARGE;
+        ret = HTTP_CONTENT_TOO_LARGE;
+        goto done;
     }
 
     /* Resource must be {accountId}/ with no trailing path */
-    char *accountid = xstrdup(txn->req_tgt.resource);
+    accountid = xstrdup(txn->req_tgt.resource);
     char *slash = strchr(accountid, '/');
     if (!slash || *(slash + 1) != '\0') {
         ret = HTTP_NOT_FOUND;
+        txn->error.desc = "unknown uploadUrl";
         goto done;
     }
     *slash = '\0';
@@ -1058,6 +1061,7 @@ static int jmap_upload(struct transaction_t *txn)
         syslog(LOG_ERR, "jmap_upload: can't open conversations db for %s: %s",
                accountid, error_message(r));
         ret = HTTP_SERVER_ERROR;
+        txn->error.desc = "can't open upload conversations db";
         goto done;
     }
 
@@ -1066,6 +1070,7 @@ static int jmap_upload(struct transaction_t *txn)
         syslog(LOG_ERR, "jmap_upload: can't open upload collection for %s: %s",
                accountid, error_message(r));
         ret = HTTP_NOT_FOUND;
+        txn->error.desc = "can't open upload collection";
         goto done;
     }
 
@@ -1197,8 +1202,15 @@ static int jmap_upload(struct transaction_t *txn)
         append_abort(&as);
         syslog(LOG_ERR, "append_fromstage(%s) failed: %s",
                mailbox_name(mailbox), error_message(r));
-        ret = HTTP_SERVER_ERROR;
-        txn->error.desc = "append_fromstage() failed";
+        if (r == IMAP_QUOTA_EXCEEDED || r == IMAP_NO_OVERQUOTA) {
+            /* XXX  Should never happen, but DTRT anyways */
+            ret = HTTP_NO_STORAGE;
+            txn->error.desc = "Mailbox is over quota";
+        }
+        else {
+            ret = HTTP_SERVER_ERROR;
+            txn->error.desc = "append_fromstage() failed";
+        }
         goto done;
     }
 
@@ -1224,6 +1236,8 @@ static int jmap_upload(struct transaction_t *txn)
     json_object_set_new(resp, "expires", json_string(datestr));
     json_object_set_new(resp, "type", json_string(normalisedtype));
 
+    ret = HTTP_CREATED;
+
 done:
     free(normalisedtype);
     free(accountid);
@@ -1250,11 +1264,29 @@ static int jmap_upload(struct transaction_t *txn)
     // checkpoint before replying
     sync_checkpoint(httpd_in);
 
-    /* Output the JSON object */
-    if (resp)
-        ret = json_response(HTTP_CREATED, txn, resp);
+    if (!resp) {
+        /* Create Problem Details Object */
+        const char *type, *limit;
 
-    return ret;
+        if (ret == HTTP_CONTENT_TOO_LARGE) {
+            type = "urn:ietf:params:jmap:error:limit";
+            limit = "maxSizeUpload";
+        }
+        else {
+            type = "about:blank";
+            limit = NULL;
+        }
+
+        resp = json_pack("{s:s s:s* s:s s:i s:s}",
+                         "type", type,
+                         "limit", limit,
+                         "title", error_message(ret) + 4,
+                         "status", atoi(error_message(ret)),
+                         "detail", txn->error.desc);
+    }
+
+    /* Output the JSON object */
+    return json_response(ret, txn, resp);
 }
 
 /* Handle a GET on the session endpoint */