diff --git a/web/database/worker/db-worker.js b/web/database/worker/db-worker.js
--- a/web/database/worker/db-worker.js
+++ b/web/database/worker/db-worker.js
@@ -1,7 +1,7 @@
 // @flow
 
 import localforage from 'localforage';
-import initSqlJs from 'sql.js';
+import initSqlJs, { type SqliteDatabase } from 'sql.js';
 
 import {
   type SharedWorkerMessageEvent,
@@ -23,7 +23,7 @@
 };
 localforage.config(localforageConfig);
 
-let sqliteDb = null;
+let sqliteDb: ?SqliteDatabase = null;
 
 async function initDatabase(sqljsFilePath: string, sqljsFilename: ?string) {
   const content = await localforage.getItem(SQLITE_CONTENT);
@@ -45,8 +45,12 @@
   }
 
   const versionData = sqliteDb.exec('PRAGMA user_version;');
-  if (versionData.length && versionData[0].values.length) {
-    console.info(`Db version: ${versionData[0].values[0]}`);
+  if (!versionData.length || !versionData[0].values.length) {
+    throw new Error('Error while retrieving database version');
+  }
+  const [dbVersion] = versionData[0].values[0];
+  if (typeof dbVersion === 'number') {
+    console.info(`Db version: ${dbVersion}`);
   } else {
     throw new Error('Error while retrieving database version');
   }
diff --git a/web/flow-typed/npm/sql.js_vx.x.x.js b/web/flow-typed/npm/sql.js_vx.x.x.js
new file mode 100644
--- /dev/null
+++ b/web/flow-typed/npm/sql.js_vx.x.x.js
@@ -0,0 +1,89 @@
+// @flow
+
+// flow-typed signature: f355493becad56880bf30832260c5460
+// flow-typed version: <<STUB>>/sql.js_v1.8.0/flow_v0.182.0
+
+declare module 'sql.js' {
+  declare export type SqlValue = number | string | Uint8Array | null;
+  declare export type ParamsObject = { +[key: string]: SqlValue };
+  declare export type ParamsCallback = (obj: ParamsObject) => void;
+
+  declare export type BindParams =
+    | $ReadOnlyArray<SqlValue>
+    | ParamsObject
+    | null;
+
+  declare export type QueryExecResult = {
+    columns: string[],
+    values: SqlValue[][],
+  };
+
+  declare export type StatementIteratorResult = {
+    +done: boolean,
+    +value: SqliteStatement,
+  };
+
+  declare export type SqlJsStatic = {
+    +Database: Class<SqliteDatabase>,
+    +Statement: Class<SqliteStatement>,
+  };
+
+  declare type EmscriptenModule = {
+    +locateFile: (path: string, prefix?: string) => string,
+    ...
+  };
+
+  declare type InitSqlJsStatic = {
+    (config?: EmscriptenModule): Promise<SqlJsStatic>,
+  };
+
+  declare export class SqliteDatabase {
+    constructor(data?: Array<number> | Uint8Array | Buffer | null): this;
+    close(): void;
+
+    create_function<T, R>(
+      name: string,
+      func: (...args: $ReadOnlyArray<T>) => R,
+    ): SqliteDatabase;
+    each(
+      sql: string,
+      params: BindParams,
+      callback: ParamsCallback,
+      done: () => void,
+    ): SqliteDatabase;
+    each(
+      sql: string,
+      callback: ParamsCallback,
+      done: () => void,
+    ): SqliteDatabase;
+    exec(sql: string, params?: BindParams): QueryExecResult[];
+    export(): Uint8Array;
+    getRowsModified(): number;
+    handleError(): null | empty;
+    iterateStatements(sql: string): StatementIterator;
+    prepare(sql: string, params?: BindParams): SqliteStatement;
+    run(sql: string, params?: BindParams): SqliteDatabase;
+  }
+
+  declare export class SqliteStatement {
+    bind(values?: BindParams): boolean;
+    free(): boolean;
+    freemem(): void;
+    get(params?: BindParams): $ReadOnlyArray<SqlValue>;
+    getAsObject(params?: BindParams): ParamsObject;
+    getColumnNames(): $ReadOnlyArray<string>;
+    getNormalizedSQL(): string;
+    getSQL(): string;
+    reset(): void;
+    run(values?: BindParams): void;
+    step(): boolean;
+  }
+
+  declare export class StatementIterator implements Iterable<SqliteStatement> {
+    @@iterator: () => Iterator<SqliteStatement>;
+    getRemainingSql(): string;
+    next(): StatementIteratorResult;
+  }
+
+  declare export default InitSqlJsStatic;
+}