diff --git a/CHANGES.md b/CHANGES.md
index 482939a..e6bdc04 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -8,6 +8,11 @@ Version 0.6.4
 
 To be released.
 
+ -  Fixed a build warning due to importing `node:fs` and `node:util` modules on
+    Next.js' client rendering.  [[#19]]
+
+[#19]: https://github.com/dahlia/logtape/issues/19
+
 
 Version 0.6.3
 -------------
diff --git a/logtape/fs.cjs b/logtape/fs.cjs
index 40171ff..fe20ac6 100644
--- a/logtape/fs.cjs
+++ b/logtape/fs.cjs
@@ -1,10 +1,12 @@
 let fs = null;
 if (
-  "process" in globalThis && "versions" in globalThis.process &&
-    "node" in globalThis.process.versions &&
-    typeof globalThis.caches === "undefined" &&
-    typeof globalThis.addEventListener !== "function" ||
-  "Bun" in globalThis
+  typeof window === "undefined" && (
+    "process" in globalThis && "versions" in globalThis.process &&
+      "node" in globalThis.process.versions &&
+      typeof globalThis.caches === "undefined" &&
+      typeof globalThis.addEventListener !== "function" ||
+    "Bun" in globalThis
+  )
 ) {
   try {
     // Intentionally confuse static analysis of bundlers:
diff --git a/logtape/nodeUtil.cjs b/logtape/nodeUtil.cjs
index dc5c169..0984aff 100644
--- a/logtape/nodeUtil.cjs
+++ b/logtape/nodeUtil.cjs
@@ -1,10 +1,12 @@
 let util = null;
 if (
-  "process" in globalThis && "versions" in globalThis.process &&
-    "node" in globalThis.process.versions &&
-    typeof globalThis.caches === "undefined" &&
-    typeof globalThis.addEventListener !== "function" ||
-  "Bun" in globalThis
+  typeof window === "undefined" && (
+    "process" in globalThis && "versions" in globalThis.process &&
+      "node" in globalThis.process.versions &&
+      typeof globalThis.caches === "undefined" &&
+      typeof globalThis.addEventListener !== "function" ||
+    "Bun" in globalThis
+  )
 ) {
   try {
     // Intentionally confuse static analysis of bundlers: