diff --git a/src/lib/utils.ts b/src/lib/utils.ts
index f0f37c59c..791e3eff4 100644
--- a/src/lib/utils.ts
+++ b/src/lib/utils.ts
@@ -47,7 +47,12 @@ export function parseRepositoryId(
 ): { prefix: string; pubkey: string } | undefined {
   const match = /^(rad:)?(z[a-zA-Z0-9]+)$/.exec(rid);
   if (match) {
-    const hex = bs58.decode(match[2].substring(1));
+    let hex: Uint8Array;
+    try {
+      hex = bs58.decode(match[2].substring(1));
+    } catch {
+      return undefined;
+    }
     if (hex.byteLength !== 20) {
       return undefined;
     }
diff --git a/tests/unit/utils.test.ts b/tests/unit/utils.test.ts
index c8996b2dd..b4f52cfea 100644
--- a/tests/unit/utils.test.ts
+++ b/tests/unit/utils.test.ts
@@ -113,12 +113,17 @@ describe("parseRepositoryId", () => {
     });
   });
 
-  test.each(["", "rad:", "rad:z3fpY7ntt", `${rid} `, "rad:x3fpY7nttPPa6MBn"])(
-    "rejects %j",
-    input => {
-      expect(parseRepositoryId(input)).toBeUndefined();
-    },
-  );
+  test.each([
+    "",
+    "rad:",
+    "rad:z3fpY7ntt",
+    `${rid} `,
+    "rad:x3fpY7nttPPa6MBn",
+    // Base58 has no 0, O, I or l.
+    "rad:z0OIl",
+  ])("rejects %j", input => {
+    expect(parseRepositoryId(input)).toBeUndefined();
+  });
 });
 
 describe("formatRepositoryId", () => {