diff --git a/packages/mermaid/src/rendering-util/svg/index.ts b/packages/mermaid/src/rendering-util/svg/index.ts
index 7a34b78e4..bc8f1c5ac 100644
--- a/packages/mermaid/src/rendering-util/svg/index.ts
+++ b/packages/mermaid/src/rendering-util/svg/index.ts
@@ -3,12 +3,14 @@ import database from "./database.js";
 import server from "./server.js";
 import disk from "./disk.js";
 import internet from "./internet.js";
+import unknown from "./unknown.js";
 
 const defaultIconLibrary: IconLibrary = {
     database: database,
     server: server,
     disk: disk,
     internet: internet,
+    unknown: unknown,
 }
 
 export default defaultIconLibrary
\ No newline at end of file
diff --git a/packages/mermaid/src/rendering-util/svg/unknown.ts b/packages/mermaid/src/rendering-util/svg/unknown.ts
new file mode 100644
index 000000000..25b1ef5c4
--- /dev/null
+++ b/packages/mermaid/src/rendering-util/svg/unknown.ts
@@ -0,0 +1,10 @@
+/**
+ * @author Nicolas Newman
+ * @see https://github.com/NicolasNewman/IconLibrary
+ */
+import { createIcon } from "../svgRegister.js";
+
+export default createIcon(`<g>
+    <rect width="80" height="80" style="fill: #087ebf; stroke-width: 0px;"/>
+    <text transform="translate(21.16 64.67)" style="fill: #fff; font-family: ArialMT, Arial; font-size: 67.75px;"><tspan x="0" y="0">?</tspan></text>
+</g>`, 80)
\ No newline at end of file
diff --git a/packages/mermaid/src/rendering-util/svgRegister.ts b/packages/mermaid/src/rendering-util/svgRegister.ts
index 4ab15b560..b5b4c5e28 100644
--- a/packages/mermaid/src/rendering-util/svgRegister.ts
+++ b/packages/mermaid/src/rendering-util/svgRegister.ts
@@ -5,6 +5,13 @@ type IconResolver = (
 ) => Selection<SVGGElement, unknown, Element | null, unknown>;
 type IconLibrary = Record<string, IconResolver>;
 
+const createIcon = (icon: string, originalSize: number): IconResolver => {
+  return (parent: Selection<SVGGElement, unknown, Element | null, unknown>, size: number = originalSize) => {
+    parent.html(`<g style="transform: scale(${size / originalSize})">${icon}</g>`)
+    return parent
+  }
+}
+
 const icons: IconLibrary = {};
 
 const isIconNameInUse = (name: string): boolean => {
@@ -29,14 +36,7 @@ const getIcon = (name: string): IconResolver | null => {
   if (isIconNameInUse(name)) {
     return icons[name];
   }
-  return null; // TODO: return default
+  return icons["unknown"];
 };
 
-const createIcon = (icon: string, originalSize: number): IconResolver => {
-  return (parent: Selection<SVGGElement, unknown, Element | null, unknown>, size: number = originalSize) => {
-    parent.html(`<g style="transform: scale(${size / originalSize})">${icon}</g>`)
-    return parent
-  }
-}
-
 export { registerIcon, registerIcons, getIcon, isIconNameInUse, createIcon, IconLibrary };