diff --git a/lib/agent/runtime.ts b/lib/agent/runtime.ts
index 83c951b..8134a54 100644
--- a/lib/agent/runtime.ts
+++ b/lib/agent/runtime.ts
@@ -167,7 +167,7 @@ export class Runtime<TState> {
 				// If the parent does not exist or the key does not exist
 				// then delete the sensor
 				if (parent == null || !Object.hasOwn(parent, Path.basename(p))) {
-					this.subscriptions[p].unsubscribe();
+					this.subscriptions[p]!.unsubscribe();
 					delete this.subscriptions[p];
 				}
 			});
diff --git a/lib/dag.ts b/lib/dag.ts
index 5654eff..9822337 100644
--- a/lib/dag.ts
+++ b/lib/dag.ts
@@ -208,6 +208,7 @@ function traverseCombine<V extends Value, T>(
 
 		assert(ends.length > 0, 'Malformed DAG found, empty Fork node');
 		const [res] = ends;
+		assert(res != null); // Typescript is not smart enough to figure out that res cannot be undefined
 		assert(!res.done, 'Malformed DAG found, disconnected fork branch');
 
 		// Combine the results from the branches passing the
diff --git a/lib/planner/findPlan.ts b/lib/planner/findPlan.ts
index 5ede66a..e3f6705 100644
--- a/lib/planner/findPlan.ts
+++ b/lib/planner/findPlan.ts
@@ -134,7 +134,7 @@ function findConflict(
 	const unique = new Map<string, [number, PatchOperation]>();
 
 	for (let i = 0; i < ops.length; i++) {
-		const patches = ops[i];
+		const patches = ops[i]!;
 
 		for (const o of patches) {
 			for (const [path, [index, op]] of unique.entries()) {
@@ -216,7 +216,7 @@ function tryParallel<TState = any>(
 	// having the fork and empty node, so we need to remove the empty node
 	// and connect the last action in the branch directly to the existing plan
 	if (results.length === 1) {
-		const branch = results[0];
+		const branch = results[0]!;
 		// Find the first node for which the next element is the
 		// empty node created earlier
 		const last = DAG.find(
diff --git a/lib/testing/builder.ts b/lib/testing/builder.ts
index 8081a19..a7838cb 100644
--- a/lib/testing/builder.ts
+++ b/lib/testing/builder.ts
@@ -68,7 +68,7 @@ function fromFork(branches: Branch[]): [Node | null, Node | null] {
 
 	// If there is only a branch, call the branch method
 	if (branches.length === 1) {
-		return fromBranch(branches[0]);
+		return fromBranch(branches[0]!);
 	}
 
 	// For multiple branches, create a fork and
diff --git a/lib/testing/mermaid.ts b/lib/testing/mermaid.ts
index 80c80c9..ad1dd3c 100644
--- a/lib/testing/mermaid.ts
+++ b/lib/testing/mermaid.ts
@@ -66,10 +66,11 @@ function fromNode(
 	if (DAG.isFork(node)) {
 		const actions = node.next.filter(PlanAction.is);
 		if (actions.length > 0) {
+			const [first] = actions;
 			// In this case we just use id of the first action in the
 			// fork as we really should not have multiple fork nodes in the
 			// diagram pointing to the same actions
-			return DiagramNode.fromId(`j${actions[0].id.substring(0, 7)}`);
+			return DiagramNode.fromId(`j${first!.id.substring(0, 7)}`);
 		}
 
 		const forks = node.next.filter(DAG.isFork);
@@ -156,7 +157,7 @@ class DiagramAdjacency {
 
 		// The official parent of a node is the last parent
 		// in the list
-		return p[p.length - 1];
+		return p[p.length - 1]!;
 	}
 
 	getAll(node: DiagramNode): DiagramNode[] {
@@ -260,7 +261,10 @@ class Diagram {
 			ends.forEach(([_, p]) => this.graph.push(`	${p} --> ${join}`));
 			this.graph.push(`	${join}:::selected`);
 
-			const [first] = ends[0];
+			const [end] = ends;
+			assert(end != null);
+
+			const [first] = end;
 
 			return this.drawPlan(first.next, join);
 		}
diff --git a/lib/utils/deep-equal.ts b/lib/utils/deep-equal.ts
index abd84bc..ed60726 100644
--- a/lib/utils/deep-equal.ts
+++ b/lib/utils/deep-equal.ts
@@ -1,3 +1,5 @@
+import { assert } from '../assert';
+
 function isObject(value: unknown): value is object {
 	return typeof value === 'object' && value !== null;
 }
@@ -33,6 +35,11 @@ export function deepEqual<T>(value: T, other: T): boolean {
 		const [vProps, oProps] = [value, other].map(
 			(a) => Object.getOwnPropertyNames(a) as Array<keyof T>,
 		);
+
+		// This will never fail but it prevents the compiler from
+		// complaining
+		assert(vProps != null && oProps != null);
+
 		if (vProps.length !== oProps.length) {
 			// If the property lists are different lengths we don't need
 			// to check any further
diff --git a/package.json b/package.json
index 66d1c53..5017458 100644
--- a/package.json
+++ b/package.json
@@ -75,7 +75,7 @@
     "tar-stream": "3.0.0",
     "ts-node": "^10.9.1",
     "tsconfig-paths": "^4.1.1",
-    "typescript": "^5.5.2"
+    "typescript": "^5.5.4"
   },
   "dependencies": {
     "mahler-wasm": "^0.1.0"
diff --git a/tsconfig.json b/tsconfig.json
index 94bbb39..160af53 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -12,6 +12,7 @@
 		"target": "es2022",
 		"declaration": true,
 		"skipLibCheck": true,
+		"noUncheckedIndexedAccess": true,
 		"paths": {
 			"mahler": [
 				"lib/index.ts"