diff --git a/src/public/app/services/content_renderer.ts b/src/public/app/services/content_renderer.ts
index ec81ef3bc..3a7c3b2e5 100644
--- a/src/public/app/services/content_renderer.ts
+++ b/src/public/app/services/content_renderer.ts
@@ -11,7 +11,7 @@ import FNote from "../entities/fnote.js";
 import FAttachment from "../entities/fattachment.js";
 import imageContextMenuService from "../menus/image_context_menu.js";
 import { applySingleBlockSyntaxHighlight, applySyntaxHighlight } from "./syntax_highlight.js";
-import { loadElkIfNeeded } from "./mermaid.js";
+import { loadElkIfNeeded, postprocessMermaidSvg } from "./mermaid.js";
 import { normalizeMimeTypeForCKEditor } from "./mime_type_definitions.js";
 
 let idCounter = 1;
@@ -226,7 +226,7 @@ async function renderMermaid(note: FNote | FAttachment, $renderedContent: JQuery
         await loadElkIfNeeded(content);
         const { svg } = await mermaid.mermaidAPI.render("in-mermaid-graph-" + idCounter++, content);
 
-        $renderedContent.append($(svg));
+        $renderedContent.append($(postprocessMermaidSvg(svg)));
     } catch (e) {
         const $error = $("<p>The diagram could not displayed.</p>");
 
diff --git a/src/public/app/services/mermaid.spec.ts b/src/public/app/services/mermaid.spec.ts
new file mode 100644
index 000000000..3da396eec
--- /dev/null
+++ b/src/public/app/services/mermaid.spec.ts
@@ -0,0 +1,35 @@
+import { describe, expect, it } from "vitest";
+import { postprocessMermaidSvg } from "./mermaid.js";
+import { trimIndentation } from "../../../../spec/support/utils.js";
+
+describe("Mermaid", () => {
+    it("converts <br> properly", () => {
+        const before = trimIndentation`\
+            <g transform="translate(-55.71875, -24)" style="color:black !important" class="label">
+            <rect></rect>
+            <foreignObject height="48" width="111.4375">
+                <div xmlns="http://www.w3.org/1999/xhtml"
+                style="color: black !important; display: table-cell; white-space: nowrap; line-height: 1.5; max-width: 200px; text-align: center;">
+                <span class="nodeLabel" style="color:black !important">
+                    <p>Verify Output<br>Against<BR > Criteria</p>
+                </span>
+                </div>
+            </foreignObject>
+            </g>
+        `;
+        const after = trimIndentation`\
+            <g transform="translate(-55.71875, -24)" style="color:black !important" class="label">
+            <rect></rect>
+            <foreignObject height="48" width="111.4375">
+                <div xmlns="http://www.w3.org/1999/xhtml"
+                style="color: black !important; display: table-cell; white-space: nowrap; line-height: 1.5; max-width: 200px; text-align: center;">
+                <span class="nodeLabel" style="color:black !important">
+                    <p>Verify Output<br/>Against<br/> Criteria</p>
+                </span>
+                </div>
+            </foreignObject>
+            </g>
+        `;
+        expect(postprocessMermaidSvg(before)).toBe(after);
+    });
+});
diff --git a/src/public/app/services/mermaid.ts b/src/public/app/services/mermaid.ts
index 3e0acca86..1100081c9 100644
--- a/src/public/app/services/mermaid.ts
+++ b/src/public/app/services/mermaid.ts
@@ -23,3 +23,16 @@ export async function loadElkIfNeeded(mermaidContent: string) {
         mermaid.registerLayoutLoaders((await import("@mermaid-js/layout-elk")).default);
     }
 }
+
+/**
+ * Processes the output of a Mermaid SVG render before it should be delivered to the user.
+ *
+ * <p>
+ * Currently this fixes <br> to <br/> which would otherwise cause an invalid XML.
+ *
+ * @param svg the Mermaid SVG to process.
+ * @returns the processed SVG.
+ */
+export function postprocessMermaidSvg(svg: string) {
+    return svg.replaceAll(/<br\s*>/ig, "<br/>");
+}
diff --git a/src/public/app/widgets/mermaid.ts b/src/public/app/widgets/mermaid.ts
index 8fcd3efdf..54f44825b 100644
--- a/src/public/app/widgets/mermaid.ts
+++ b/src/public/app/widgets/mermaid.ts
@@ -3,7 +3,7 @@ import libraryLoader from "../services/library_loader.js";
 import NoteContextAwareWidget from "./note_context_aware_widget.js";
 import server from "../services/server.js";
 import utils from "../services/utils.js";
-import { loadElkIfNeeded } from "../services/mermaid.js";
+import { loadElkIfNeeded, postprocessMermaidSvg } from "../services/mermaid.js";
 import type FNote from "../entities/fnote.js";
 import type { EventData } from "../components/app_context.js";
 
@@ -122,7 +122,7 @@ export default class MermaidWidget extends NoteContextAwareWidget {
 
         await loadElkIfNeeded(content);
         const { svg } = await mermaid.mermaidAPI.render(`mermaid-graph-${idCounter}`, content);
-        return svg;
+        return postprocessMermaidSvg(svg);
     }
 
     async entitiesReloadedEvent({ loadResults }: EventData<"entitiesReloaded">) {