diff --git a/schemes/main/manifest.json b/schemes/main/manifest.json
index a000795c..3f5998f2 100644
--- a/schemes/main/manifest.json
+++ b/schemes/main/manifest.json
@@ -1,5 +1,5 @@
 {
-  "base-tag": "swift-DEVELOPMENT-SNAPSHOT-2025-04-03-a",
+  "base-tag": "swift-DEVELOPMENT-SNAPSHOT-2025-04-12-a",
   "icu4c": [],
   "libxml2": [
     "https://github.com/swiftwasm/libxml2-wasm/releases/download/2.0.0/libxml2-wasm32-unknown-wasi.tar.gz",
diff --git a/schemes/main/swift-foundation/0001-wasm-Stop-requiring-TZDIR-and-TZDEFAULT-on-WASI.patch b/schemes/main/swift-foundation/0001-wasm-Stop-requiring-TZDIR-and-TZDEFAULT-on-WASI.patch
new file mode 100644
index 00000000..1cb76e7d
--- /dev/null
+++ b/schemes/main/swift-foundation/0001-wasm-Stop-requiring-TZDIR-and-TZDEFAULT-on-WASI.patch
@@ -0,0 +1,27 @@
+From 3828fe6d24735d59d53f073d9021b954d28e5750 Mon Sep 17 00:00:00 2001
+From: Yuta Saito <kateinoigakukun@gmail.com>
+Date: Mon, 14 Apr 2025 18:20:25 +0000
+Subject: [PATCH] [wasm] Stop requiring `TZDIR` and `TZDEFAULT` on WASI
+
+Those constants are not used on WASI in Swift side, so there's no
+need to require them in the C headers.
+---
+ Sources/_FoundationCShims/include/_CStdlib.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/Sources/_FoundationCShims/include/_CStdlib.h b/Sources/_FoundationCShims/include/_CStdlib.h
+index 405febc..408a924 100644
+--- a/Sources/_FoundationCShims/include/_CStdlib.h
++++ b/Sources/_FoundationCShims/include/_CStdlib.h
+@@ -156,7 +156,7 @@
+ #ifndef TZDEFAULT
+ #define TZDEFAULT    "/etc/localtime"
+ #endif /* !defined TZDEFAULT */
+-#elif TARGET_OS_WINDOWS
++#elif TARGET_OS_WINDOWS || TARGET_OS_WASI
+ /* not required */
+ #else
+ #error "possibly define TZDIR and TZDEFAULT for this platform"
+-- 
+2.48.1
+
diff --git a/test/lit.cfg b/test/lit.cfg
index e4ffa1e0..0e5ca24d 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -21,7 +21,11 @@ config.test_exec_root = lit_config.params.get(
     "/tmp/swift-extra-integration-tests")
 
 config.available_features.add("platform="+platform.system())
-config.available_features.add("scheme="+lit_config.params.get("scheme", "main"))
+
+# --param scheme=<scheme>
+scheme = lit_config.params.get("scheme", "main")
+config.scheme = scheme
+config.available_features.add("scheme="+scheme)
 
 # --param swift-sdk=<swift-sdk-id>
 swift_sdk = lit_config.params.get("swift-sdk")
diff --git a/test/swift-sdk/lit.local.cfg b/test/swift-sdk/lit.local.cfg
index df5019d3..81cb5236 100644
--- a/test/swift-sdk/lit.local.cfg
+++ b/test/swift-sdk/lit.local.cfg
@@ -15,11 +15,15 @@ else:
     target_swift_build = f"{swift} build {swift_sdk_options}"
     config.substitutions.append(("%{target_swift_build}", target_swift_build))
 
+    copy_cmd = 'cp %s %t.dir/Sources/Check/Check.swift'
+    if config.root.scheme in ["release-6.0", "release-6.1", "release-6.2"]:
+        copy_cmd = 'cp %s %t.dir/Sources/main.swift'
+
     simple_swift_build_steps = [
         'rm -rf %t.dir',
         'mkdir -p %t.dir',
         f'{swift} package init --package-path %t.dir --name Check --type executable',
-        'cp %s %t.dir/Sources/main.swift',
+        copy_cmd,
         f'{target_swift_build} --package-path %t.dir',
     ]
     config.substitutions.append(("%{target_simple_swift_build}", " && ".join(simple_swift_build_steps)))