diff --git a/uuid/mod.ts b/uuid/mod.ts
index c3ab445504fe..2d676a9dd113 100644
--- a/uuid/mod.ts
+++ b/uuid/mod.ts
@@ -76,5 +76,5 @@ export function version(uuid: string): number {
     throw new TypeError("Invalid UUID");
   }
 
-  return parseInt(uuid[14], 16);
+  return parseInt(uuid[14]!, 16);
 }
diff --git a/uuid/v1.ts b/uuid/v1.ts
index 55a928bf229b..d9d34d40deb0 100644
--- a/uuid/v1.ts
+++ b/uuid/v1.ts
@@ -136,6 +136,12 @@ export function generate(
     throw new Error("Can't create more than 10M uuids/sec");
   }
 
+  if (node.length !== 6) {
+    throw new Error(
+      "Cannot create UUID. The node option must be an array of 6 bytes",
+    );
+  }
+
   _lastMSecs = msecs;
   _lastNSecs = nsecs;
   _clockseq = clockseq;
@@ -163,7 +169,7 @@ export function generate(
   b[i++] = clockseq & 0xff;
 
   for (let n = 0; n < 6; ++n) {
-    b[i + n] = node[n];
+    b[i + n] = node[n]!;
   }
 
   return buf ?? bytesToUuid(b);
diff --git a/uuid/v1_test.ts b/uuid/v1_test.ts
index 818498d9207b..c10600e19019 100644
--- a/uuid/v1_test.ts
+++ b/uuid/v1_test.ts
@@ -59,6 +59,26 @@ Deno.test("generate() can fill the UUID into a buffer", () => {
   assertEquals(buf, uuid);
 });
 
+Deno.test("generate() throws when node is passed with less than 6 numbers", () => {
+  assertThrows(
+    () => {
+      generate({ node: [0x01, 0x23, 0x45, 0x67, 0x89] });
+    },
+    Error,
+    "Cannot create UUID. The node option must be an array of 6 bytes",
+  );
+});
+
+Deno.test("generate() throws when node is passed with more than 6 numbers", () => {
+  assertThrows(
+    () => {
+      generate({ node: [0x01, 0x23, 0x45, 0x67, 0x89, 0x89, 0x89] });
+    },
+    Error,
+    "Cannot create UUID. The node option must be an array of 6 bytes",
+  );
+});
+
 Deno.test("generate() throws when create more than 10M uuids/sec", () => {
   assertThrows(
     () => {
diff --git a/uuid/v3.ts b/uuid/v3.ts
index 466314f1bb12..8733dc3f7b10 100644
--- a/uuid/v3.ts
+++ b/uuid/v3.ts
@@ -54,8 +54,8 @@ export async function generate(
   const buffer = await crypto.subtle.digest("MD5", toHash);
   const bytes = new Uint8Array(buffer);
 
-  bytes[6] = (bytes[6] & 0x0f) | 0x30;
-  bytes[8] = (bytes[8] & 0x3f) | 0x80;
+  bytes[6] = (bytes[6]! & 0x0f) | 0x30;
+  bytes[8] = (bytes[8]! & 0x3f) | 0x80;
 
   return bytesToUuid(bytes);
 }
diff --git a/uuid/v5.ts b/uuid/v5.ts
index 539580cbb4c6..8ad85ce083f9 100644
--- a/uuid/v5.ts
+++ b/uuid/v5.ts
@@ -53,8 +53,8 @@ export async function generate(
   const buffer = await crypto.subtle.digest("sha-1", toHash);
   const bytes = new Uint8Array(buffer);
 
-  bytes[6] = (bytes[6] & 0x0f) | 0x50;
-  bytes[8] = (bytes[8] & 0x3f) | 0x80;
+  bytes[6] = (bytes[6]! & 0x0f) | 0x50;
+  bytes[8] = (bytes[8]! & 0x3f) | 0x80;
 
   return bytesToUuid(bytes);
 }