diff --git a/e2e-tests/Dockerfile b/e2e-tests/Dockerfile
index 6daa755..37132f7 100644
--- a/e2e-tests/Dockerfile
+++ b/e2e-tests/Dockerfile
@@ -8,6 +8,8 @@ COPY e2e-tests/package.json e2e-tests/package-lock.json ./
 RUN npm ci
 
 COPY e2e-tests/ ./
+# e2e-tests/tsconfig.json extends it, so the specs are held to the host's strictness flags.
+COPY tsconfig.json /tsconfig.json
 
 # Runs as the invoking `--user` so artifacts land owned by them, not root — and an arbitrary uid has
 # no passwd entry here, so its home would be the unwritable `/`. npm's cache follows HOME.
diff --git a/e2e-tests/tsconfig.json b/e2e-tests/tsconfig.json
index d2dc2a8..5e06753 100644
--- a/e2e-tests/tsconfig.json
+++ b/e2e-tests/tsconfig.json
@@ -1,28 +1,5 @@
 {
-  "compilerOptions": {
-    "lib": ["ESNext", "DOM"],
-    "module": "NodeNext",
-    "moduleResolution": "NodeNext",
-    "target": "ESNext",
-    "types": ["node"],
-
-    "allowImportingTsExtensions": true,
-    "erasableSyntaxOnly": true,
-    "isolatedModules": true,
-    "noEmit": true,
-    "verbatimModuleSyntax": true,
-
-    "strict": true,
-    "exactOptionalPropertyTypes": true,
-    "noFallthroughCasesInSwitch": true,
-    "noImplicitOverride": true,
-    "noImplicitReturns": true,
-    "noUncheckedIndexedAccess": true,
-    "noUnusedLocals": true,
-    "noUnusedParameters": true,
-
-    "forceConsistentCasingInFileNames": true,
-    "skipLibCheck": true
-  },
+  "extends": "../tsconfig.json",
+  "compilerOptions": { "lib": ["ESNext", "DOM"] },
   "include": ["*.ts"]
 }