diff --git a/src/client.js b/src/client.js
index 79731af6f..cf539bf7c 100644
--- a/src/client.js
+++ b/src/client.js
@@ -537,16 +537,18 @@ export class StreamChat {
 		let fileField;
 
 		const params = this._addClientParams();
-		if (isReadableStream(uri) || uri instanceof File) {
+		const isFileWebAPI = input =>
+			typeof window !== 'undefined' && 'File' in window && input instanceof File;
+		if (isReadableStream(uri) || isFileWebAPI(uri)) {
 			fileField = uri;
 		} else {
 			fileField = {
 				uri,
 				name: name || uri.split('/').reverse()[0],
 			};
-			if (contentType != null) {
-				fileField.type = contentType;
-			}
+		}
+		if (contentType != null) {
+			fileField.type = contentType;
 		}
 
 		if (user != null) {