diff --git a/.changeset/sequelize-keeps-its-ssl-options.md b/.changeset/sequelize-keeps-its-ssl-options.md
new file mode 100644
index 0000000..677ad1c
--- /dev/null
+++ b/.changeset/sequelize-keeps-its-ssl-options.md
@@ -0,0 +1,12 @@
+---
+'seamless-auth-api': patch
+---
+
+Keep the TLS options when `DATABASE_URL` carries `sslmode`. `resolveSslOptions` turns `DB_SSL`,
+or an `sslmode` on the connection string, into Sequelize's `dialectOptions.ssl`, but Sequelize
+then read the same `sslmode` for itself and let pg-connection-string's reading of it replace
+those options. A URL carrying the parameter had its certificate verified whatever `DB_SSL` or
+`DB_SSL_REJECT_UNAUTHORIZED` said, which against Amazon RDS is a boot failure, and `DB_SSL=false`
+could not turn TLS off for it. Sequelize is now constructed with `sslmode` taken out of the URL,
+once `resolveSslOptions` has read it. Nothing changes on the discrete `DB_*` path, whose URL
+never carries the parameter.
diff --git a/src/config/database.cjs b/src/config/database.cjs
index 6b91317..105fa47 100644
--- a/src/config/database.cjs
+++ b/src/config/database.cjs
@@ -103,9 +103,29 @@ function resolveSslOptions(url) {
   return ca ? { ca, rejectUnauthorized } : { rejectUnauthorized };
 }
 
+// The connection string to construct Sequelize with. Sequelize reads the query of a
+// connection string for itself and lets pg-connection-string's reading of `sslmode`
+// replace the `ssl` it was given in `dialectOptions`, so with `sslmode` on the URL the
+// options above would be thrown away and the certificate verified whatever `DB_SSL` or
+// `DB_SSL_REJECT_UNAUTHORIZED` said. `resolveSslOptions` has read `sslmode` by then, so
+// it comes out of the URL here. Migrations are not affected: config.cjs hands
+// sequelize-cli discrete fields, never the string.
+function withoutSslMode(url) {
+  const query = url.indexOf('?');
+  if (query === -1) return url;
+
+  const params = new URLSearchParams(url.slice(query + 1));
+  if (!params.has('sslmode')) return url;
+
+  params.delete('sslmode');
+  const rest = params.toString();
+  return rest ? `${url.slice(0, query)}?${rest}` : url.slice(0, query);
+}
+
 module.exports = {
   buildDatabaseUrl,
   parseDatabaseUrl,
   resolveDatabaseUrl,
   resolveSslOptions,
+  withoutSslMode,
 };
diff --git a/src/config/database.d.cts b/src/config/database.d.cts
index f62bf2f..3f67f83 100644
--- a/src/config/database.d.cts
+++ b/src/config/database.d.cts
@@ -21,3 +21,4 @@ export declare function buildDatabaseUrl(): string;
 export declare function parseDatabaseUrl(url: string): DatabaseConnection | null;
 export declare function resolveDatabaseUrl(): string | null;
 export declare function resolveSslOptions(url: string | null): DatabaseSslOptions | null;
+export declare function withoutSslMode(url: string): string;
diff --git a/src/models/index.ts b/src/models/index.ts
index 3cd735f..c6003fe 100644
--- a/src/models/index.ts
+++ b/src/models/index.ts
@@ -9,7 +9,7 @@ import path from 'path';
 import { Sequelize } from 'sequelize';
 import { fileURLToPath } from 'url';
 
-import { buildDatabaseUrl, resolveSslOptions } from '../config/database.cjs';
+import { buildDatabaseUrl, resolveSslOptions, withoutSslMode } from '../config/database.cjs';
 import getLogger from '../utils/logger.js';
 
 const logger = getLogger('sequelize');
@@ -42,7 +42,7 @@ export function getSequelize(): Sequelize {
 
   logger.info(`Using Postgres database (TLS ${ssl ? 'enabled' : 'disabled'})`);
 
-  sequelizeInstance = new Sequelize(DATABASE_URL, {
+  sequelizeInstance = new Sequelize(withoutSslMode(DATABASE_URL), {
     logging: enableDbLogging ? (msg) => logger.debug(msg) : false,
     ...(ssl ? { dialectOptions: { ssl } } : {}),
   });
diff --git a/tests/unit/config/database.spec.ts b/tests/unit/config/database.spec.ts
index 79b5bbb..cfc3f32 100644
--- a/tests/unit/config/database.spec.ts
+++ b/tests/unit/config/database.spec.ts
@@ -6,6 +6,7 @@ import {
   parseDatabaseUrl,
   resolveDatabaseUrl,
   resolveSslOptions,
+  withoutSslMode,
 } from '../../../src/config/database.cjs';
 
 const DB_VARS = [
@@ -193,3 +194,25 @@ describe('sequelize-cli config', () => {
     });
   });
 });
+
+describe('withoutSslMode', () => {
+  it('takes sslmode out and leaves the credentials and other parameters as they were', () => {
+    expect(
+      withoutSslMode(
+        'postgres://auth:p%40ss@db.internal:5432/auth_db?sslmode=require&application_name=auth',
+      ),
+    ).toBe('postgres://auth:p%40ss@db.internal:5432/auth_db?application_name=auth');
+  });
+
+  it('leaves no trailing query behind when sslmode was the only parameter', () => {
+    expect(withoutSslMode('postgres://auth@db.internal:5432/auth_db?sslmode=require')).toBe(
+      'postgres://auth@db.internal:5432/auth_db',
+    );
+  });
+
+  it('returns a string without sslmode untouched', () => {
+    expect(withoutSslMode('postgres://auth@db.internal:5432/auth_db')).toBe(
+      'postgres://auth@db.internal:5432/auth_db',
+    );
+  });
+});
diff --git a/tests/unit/models/sequelize.spec.ts b/tests/unit/models/sequelize.spec.ts
index d0f5ccd..858fd7c 100644
--- a/tests/unit/models/sequelize.spec.ts
+++ b/tests/unit/models/sequelize.spec.ts
@@ -85,15 +85,17 @@ describe('getSequelize database URL building', () => {
     );
   });
 
-  it('uses DB_URI when DATABASE_URL is unset', async () => {
+  it('uses DB_URI when DATABASE_URL is unset, with its sslmode read and then taken out', async () => {
     process.env.DB_URI = 'postgres://user:pass@example.com:5432/auth_db?sslmode=verify-full';
 
     const { getSequelize } = await import('../../../src/models/index.js');
 
     getSequelize();
 
+    // Sequelize would read the sslmode itself and overwrite dialectOptions.ssl with
+    // pg-connection-string's version, so the URL it gets no longer carries it.
     expect(sequelizeConstructor).toHaveBeenCalledWith(
-      process.env.DB_URI,
+      'postgres://user:pass@example.com:5432/auth_db',
       expect.objectContaining({
         dialectOptions: { ssl: { rejectUnauthorized: true } },
       }),