diff --git a/api.js b/api.js
index dcb81af..7a8b677 100644
--- a/api.js
+++ b/api.js
@@ -1,3 +1,10 @@
+/**
+ * Thrown when the response is technically a "success" one, but the returned data is not what it should be.
+ */
+
+class ResponseDataError extends Error {}
+
+
 /**
  * Thrown when the passed URL is not a supported post URL on bsky.app.
  */
@@ -145,15 +152,20 @@ class BlueskyAPI extends Minisky {
   /** @param {string} handle, @returns {Promise<string>} */
 
   async resolveHandle(handle) {
-    let did = this.handleCache.getHandleDid(handle);
+    let cachedDid = this.handleCache.getHandleDid(handle);
 
-    if (did) {
-      return did;
+    if (cachedDid) {
+      return cachedDid;
     } else {
       let json = await this.getRequest('com.atproto.identity.resolveHandle', { handle }, { auth: false });
-      did = json['did'];
-      this.handleCache.setHandleDid(handle, did);
-      return did;
+      let did = json['did'];
+
+      if (did) {
+        this.handleCache.setHandleDid(handle, did);
+        return did;        
+      } else {
+        throw new ResponseDataError('Missing DID in response: ' + JSON.stringify(json));
+      }
     }
   }
 
diff --git a/jsconfig.json b/jsconfig.json
index cd4b961..772516a 100644
--- a/jsconfig.json
+++ b/jsconfig.json
@@ -3,7 +3,9 @@
     "target": "es2022",
     "checkJs": true,
     "strict": true,
-    "noImplicitAny": false
+    "noImplicitAny": false,
+    "exactOptionalPropertyTypes": true,
+    "useUnknownInCatchVariables": false
   },
   "include": ["*.js", "*.d.ts"]
 }
diff --git a/skythread.js b/skythread.js
index 0c52361..ced6999 100644
--- a/skythread.js
+++ b/skythread.js
@@ -1,7 +1,6 @@
 function init() {
-  /** @type {AnyElement} */
-  let document = window.document;
-  let html = document.body.parentNode;
+  let document = /** @type {AnyElement} */ (/** @type {unknown} */ (window.document));
+  let html = /** @type {AnyElement} */ (/** @type {unknown} */ (window.document.body.parentNode));
 
   window.dateLocale = localStorage.getItem('locale') || undefined;
 
diff --git a/types.d.ts b/types.d.ts
index 7edf972..fbe11c8 100644
--- a/types.d.ts
+++ b/types.d.ts
@@ -1,7 +1,7 @@
 interface Window {
   unauthed: boolean;
   root: AnyPost;
-  dateLocale?: string;
+  dateLocale: string | undefined;
 }
 
 declare var api: BlueskyAPI;