diff --git a/src/app/ui/file_selector.cpp b/src/app/ui/file_selector.cpp
index 9c5b0c08b..9992d4e1b 100644
--- a/src/app/ui/file_selector.cpp
+++ b/src/app/ui/file_selector.cpp
@@ -547,6 +547,18 @@ std::string FileSelector::show(
     }
     // else file-name specified in the entry is really a file to open...
 
+    if (m_type == FileSelectorType::Save) {
+      std::string finalFilename = base::get_file_name(buf);
+      if (const size_t fver = base::verify_filename(finalFilename); fver != std::string::npos)
+      {
+        Alert::show("Error<<Invalid filename: \"%s\"<<The name contains an invalid '%c' character.||&Go back",
+          finalFilename.c_str(), finalFilename[fver]);
+
+        setVisible(true);
+        goto again;
+      }
+    }
+
     // does it not have extension? ...we should add the extension
     // selected in the filetype combo-box
     if (base::get_file_extension(buf).empty()) {
@@ -741,6 +753,17 @@ void FileSelector::onNewFolder()
     if (currentFolder) {
       std::string dirname = window.name()->text();
 
+      if (m_type == FileSelectorType::Save) {
+        if (const size_t fver = base::verify_filename(dirname); fver != std::string::npos)
+        {
+          Alert::show("Error<<Invalid folder name: \"%s\"<<The name contains an invalid '%c' character.||&OK",
+            dirname.c_str(), dirname[fver]);
+
+          setVisible(true);
+          return;
+        }
+      }
+
       // Create the new directory
       try {
         currentFolder->createDirectory(dirname);
diff --git a/src/base/path.cpp b/src/base/path.cpp
index 319e96bb2..478434da4 100644
--- a/src/base/path.cpp
+++ b/src/base/path.cpp
@@ -1,5 +1,6 @@
-// Aseprite Base Library
-// Copyright (c) 2001-2016 David Capello
+// Base Library
+// Aseprite    | Copyright (C) 2001-2016  David Capello
+// LibreSprite | Copyright (C) 2026       LibreSprite contributors
 //
 // This file is released under the terms of the MIT license.
 // Read LICENSE.txt for more information.
@@ -243,4 +244,20 @@ int compare_filenames(const std::string& a, const std::string& b)
     return 1;
 }
 
+size_t verify_filename(const std::string& filename)
+{
+#ifdef _WIN32
+  // In general, _wfopen() would fail for most of these characters *except slashes and colon*,
+  // but returning a meaningful error message to the user is always a nice practice.
+  const std::string invalidChars = ":?\"<>|*";
+
+  for (size_t it=0; it<filename.size(); ++it) {
+    if (invalidChars.find(filename[it]) != std::string::npos) {
+      return it;
+    }
+  }
+#endif
+  return std::string::npos;
+}
+
 } // namespace base
diff --git a/src/base/path.h b/src/base/path.h
index 8af3ba0a9..cbda86e42 100644
--- a/src/base/path.h
+++ b/src/base/path.h
@@ -1,5 +1,6 @@
-// Aseprite Base Library
-// Copyright (c) 2001-2016 David Capello
+// Base Library
+// Aseprite    | Copyright (C) 2001-2016  David Capello
+// LibreSprite | Copyright (C) 2026       LibreSprite contributors
 //
 // This file is released under the terms of the MIT license.
 // Read LICENSE.txt for more information.
@@ -52,4 +53,8 @@ namespace base {
 
   int compare_filenames(const std::string& a, const std::string& b);
 
+  // Does platform-specific filename pre-validation to avoid any unexpected
+  // edge-case behaviors caused by feeding unsolicited parameters to stdio API
+  // (like ':' for addressing alternate NTFS streams on Windows)
+  size_t verify_filename(const std::string& filename);
 }