diff --git a/js/components/Apple2.tsx b/js/components/Apple2.tsx
index 1ff23de..9d36a67 100644
--- a/js/components/Apple2.tsx
+++ b/js/components/Apple2.tsx
@@ -41,7 +41,7 @@ export const Apple2 = (props: Apple2Props) => {
     const [apple2, setApple2] = useState<Apple2Impl>();
     const [io, setIO] = useState<Apple2IO>();
     const [cpu, setCPU] = useState<CPU6502>();
-    const [error, setError] = useState<string>();
+    const [error, setError] = useState<unknown>();
 
     useEffect(() => {
         if (screen.current) {
@@ -59,13 +59,7 @@ export const Apple2 = (props: Apple2Props) => {
                 setCPU(cpu);
                 apple2.reset();
                 apple2.run();
-            }).catch((e) => {
-                if (e instanceof Error) {
-                    setError(e.message);
-                } else {
-                    console.error(e);
-                }
-            });
+            }).catch((e) => setError(e));
         }
     }, [props]);
 
diff --git a/js/components/DiskII.tsx b/js/components/DiskII.tsx
index d22a275..e622a3e 100644
--- a/js/components/DiskII.tsx
+++ b/js/components/DiskII.tsx
@@ -40,19 +40,11 @@ export interface DiskIIProps extends DiskIIData {
 export const DiskII = ({ disk2, number, on, name, side }: DiskIIProps) => {
     const label = side ? `${name} - ${side}` : name;
     const [modalOpen, setModalOpen] = useState(false);
-    const [error, setError] = useState<string>();
+    const [error, setError] = useState<unknown>();
     const [currentHash, setCurrentHash] = useState<string>();
 
     const hash = useHash();
 
-    const handleError = (e: unknown) => {
-        if (e instanceof Error) {
-            setError(e.message);
-        } else {
-            console.error(e);
-        }
-    };
-
     useEffect(() => {
         const hashParts = getHashParts(hash);
         const newHash = hashParts[number];
@@ -61,11 +53,11 @@ export const DiskII = ({ disk2, number, on, name, side }: DiskIIProps) => {
             if (hashPart !== currentHash) {
                 if (hashPart.match(/^https?:/)) {
                     loadHttpFile(disk2, number, hashPart)
-                        .catch((e) => handleError(e));
+                        .catch((e) => setError(e));
                 } else {
                     const filename = `/json/disks/${hashPart}.json`;
                     loadJSON(disk2, number, filename)
-                        .catch((e) => handleError(e));
+                        .catch((e) => setError(e));
                 }
                 setCurrentHash(hashPart);
             }
diff --git a/js/components/ErrorModal.tsx b/js/components/ErrorModal.tsx
index dea54c4..0e58d1c 100644
--- a/js/components/ErrorModal.tsx
+++ b/js/components/ErrorModal.tsx
@@ -1,34 +1,45 @@
-import { h, Fragment } from 'preact';
+import { h } from 'preact';
 import { useCallback } from 'preact/hooks';
 import { Modal, ModalContent, ModalFooter } from './Modal';
 
 export interface ErrorProps {
-    error: string | undefined;
+    error: unknown | undefined;
     setError: (error: string | undefined) => void;
 }
 
-export const ErrorModal = ({ error, setError } : ErrorProps) => {
+export const ErrorModal = ({ error, setError }: ErrorProps) => {
     const onClose = useCallback(() => setError(undefined), [setError]);
+    let errorStr = null;
+    if (error) {
+        if (error instanceof Error) {
+            errorStr = error.message;
+        } else if (typeof error === 'string') {
+            errorStr = error;
+        } else {
+            errorStr = 'Unknown Error';
+            console.error(error);
+        }
+    }
 
-    return (
-        <>
-            { error && (
-                <Modal
-                    title="Error"
-                    icon="triangle-exclamation"
-                    isOpen={true}
-                    onClose={onClose}
-                >
-                    <ModalContent>
-                        <div style={{ width: 320, fontSize: '1.1em', padding: '5px 11px'}}>
-                            {error}
-                        </div>
-                    </ModalContent>
-                    <ModalFooter>
-                        <button onClick={onClose}>OK</button>
-                    </ModalFooter>
-                </Modal>
-            )}
-        </>
-    );
+    if (errorStr) {
+        return (
+            <Modal
+                title="Error"
+                icon="triangle-exclamation"
+                isOpen={true}
+                onClose={onClose}
+            >
+                <ModalContent>
+                    <div style={{ width: 320, fontSize: '1.1em', padding: '5px 11px' }}>
+                        {errorStr}
+                    </div>
+                </ModalContent>
+                <ModalFooter>
+                    <button onClick={onClose}>OK</button>
+                </ModalFooter>
+            </Modal>
+        );
+    } else {
+        return null;
+    }
 };
diff --git a/js/components/FileModal.tsx b/js/components/FileModal.tsx
index 3c4ace4..243bacb 100644
--- a/js/components/FileModal.tsx
+++ b/js/components/FileModal.tsx
@@ -52,7 +52,7 @@ export const FileModal = ({ disk2, number, onClose, isOpen }: FileModalProps) =>
     const [category, setCategory] = useState<string>();
     const [handles, setHandles] = useState<FileSystemFileHandleLike[]>();
     const [filename, setFilename] = useState<string>();
-    const [error, setError] = useState<string>();
+    const [error, setError] = useState<unknown>();
     const hash = useHash();
 
     const doCancel = useCallback(() => onClose(true), [onClose]);
@@ -72,11 +72,7 @@ export const FileModal = ({ disk2, number, onClose, isOpen }: FileModalProps) =>
                 await loadJSON(disk2, number, filename);
             }
         } catch (e) {
-            if (e instanceof Error) {
-                setError(e.message);
-            } else {
-                console.error(e);
-            }
+            setError(e);
         } finally {
             setHashParts(hashParts);
             setBusy(false);
diff --git a/js/formats/woz.ts b/js/formats/woz.ts
index cd90f2f..12eeb60 100644
--- a/js/formats/woz.ts
+++ b/js/formats/woz.ts
@@ -19,10 +19,10 @@ const WOZ_INTEGRITY_CHECK = 0x0a0d0aff;
  * @returns ASCII string
  */
 function stringFromBytes(data: DataView, start: number, end: number): string {
-    return String.fromCharCode.apply(
-        null,
-        new Uint8Array(data.buffer.slice(data.byteOffset + start, data.byteOffset + end))
-    ) as string;
+    const byteArray = new Uint8Array(
+        data.buffer.slice(data.byteOffset + start, data.byteOffset + end)
+    );
+    return String.fromCharCode(...byteArray);
 }
 
 export class InfoChunk {
diff --git a/js/ui/apple2.ts b/js/ui/apple2.ts
index e47572a..91050ef 100644
--- a/js/ui/apple2.ts
+++ b/js/ui/apple2.ts
@@ -622,7 +622,7 @@ function loadDisk(drive: DriveNumber, disk: JSONDisk) {
  */
 
 function updateLocalStorage() {
-    const diskIndex = JSON.parse(window.localStorage.diskIndex as string || '{}') as LocalDiskIndex;
+    const diskIndex = JSON.parse(window.localStorage.getItem('diskIndex') || '{}') as LocalDiskIndex;
     const names = Object.keys(diskIndex);
 
     const cat: DiskDescriptor[] = disk_categories['Local Saves'] = [];
@@ -654,12 +654,12 @@ type LocalDiskIndex = {
 };
 
 function saveLocalStorage(drive: DriveNumber, name: string) {
-    const diskIndex = JSON.parse(window.localStorage.diskIndex as string || '{}') as LocalDiskIndex;
+    const diskIndex = JSON.parse(window.localStorage.getItem('diskIndex') || '{}') as LocalDiskIndex;
 
     const json = _disk2.getJSON(drive);
     diskIndex[name] = json;
 
-    window.localStorage.diskIndex = JSON.stringify(diskIndex);
+    window.localStorage.setItem('diskIndex',  JSON.stringify(diskIndex));
 
     driveLights.label(drive, name);
     driveLights.dirty(drive, false);
@@ -667,17 +667,17 @@ function saveLocalStorage(drive: DriveNumber, name: string) {
 }
 
 function deleteLocalStorage(name: string) {
-    const diskIndex = JSON.parse(window.localStorage.diskIndex as string || '{}') as LocalDiskIndex;
+    const diskIndex = JSON.parse(window.localStorage.getItem('diskIndex') || '{}') as LocalDiskIndex;
     if (diskIndex[name]) {
         delete diskIndex[name];
         openAlert('Deleted');
     }
-    window.localStorage.diskIndex = JSON.stringify(diskIndex);
+    window.localStorage.setItem('diskIndex',  JSON.stringify(diskIndex));
     updateLocalStorage();
 }
 
 function loadLocalStorage(drive: DriveNumber, name: string) {
-    const diskIndex = JSON.parse(window.localStorage.diskIndex as string || '{}') as LocalDiskIndex;
+    const diskIndex = JSON.parse(window.localStorage.getItem('diskIndex') || '{}') as LocalDiskIndex;
     if (diskIndex[name]) {
         _disk2.setJSON(drive, diskIndex[name]);
         driveLights.label(drive, name);
@@ -887,11 +887,12 @@ function onLoaded(apple2: Apple2, disk2: DiskII, massStorage: MassStorage, print
     keyboard.setFunction('F3', () => io.keyDown(0x1b)); // Escape
     keyboard.setFunction('F4', optionsModal.openModal);
     keyboard.setFunction('F6', () => {
-        window.localStorage.state = base64_json_stringify(_apple2.getState());
+        window.localStorage.setItem('state', base64_json_stringify(_apple2.getState()));
     });
     keyboard.setFunction('F9', () => {
-        if (window.localStorage.state) {
-            _apple2.setState(base64_json_parse(window.localStorage.state as string) as Apple2State);
+        const localState = window.localStorage.getItem('state');
+        if (localState) {
+            _apple2.setState(base64_json_parse(localState) as Apple2State);
         }
     });
 
diff --git a/test/components/ErrorModal.spec.tsx b/test/components/ErrorModal.spec.tsx
index 2e23de4..d11a7ff 100644
--- a/test/components/ErrorModal.spec.tsx
+++ b/test/components/ErrorModal.spec.tsx
@@ -9,7 +9,17 @@ describe('ErrorModal', () => {
     it('renders when there is an error', () => {
         const setError = jest.fn();
         render(
-            <ErrorModal error="My Error" setError={setError} />
+            <ErrorModal error={new Error('My Error')} setError={setError} />
+        );
+        expect(screen.queryByRole('banner')).toBeVisible();
+        expect(screen.queryByRole('banner')).toHaveTextContent('Error');
+        expect(screen.queryByText('My Error')).toBeVisible();
+    });
+
+    it('renders when there is an error string', () => {
+        const setError = jest.fn();
+        render(
+            <ErrorModal error={'My Error'} setError={setError} />
         );
         expect(screen.queryByRole('banner')).toBeVisible();
         expect(screen.queryByRole('banner')).toHaveTextContent('Error');
@@ -18,11 +28,20 @@ describe('ErrorModal', () => {
 
     it('does not render when there is not an error', () => {
         const setError = jest.fn();
-        render(
+        const { container } = render(
             <ErrorModal error={undefined} setError={setError} />
         );
-        expect(screen.queryByRole('banner')).not.toBeInTheDocument();
-        expect(screen.queryByText('My Error')).not.toBeInTheDocument();
+        expect(container).toBeEmptyDOMElement();
+    });
+
+    it('handles an invalid error', () => {
+        jest.spyOn(console, 'error').mockImplementation();
+        const setError = jest.fn();
+        render(
+            <ErrorModal error={{foo: 'My Error'}} setError={setError} />
+        );
+        expect(screen.queryByText('Unknown Error')).toBeVisible();
+        expect(console.error).toHaveBeenCalledWith({foo: 'My Error'});
     });
 
     it('calls setError when close is clicked', () => {