diff --git a/src/network/CrossPointWebServer.cpp b/src/network/CrossPointWebServer.cpp
index b869398..90dfed7 100644
--- a/src/network/CrossPointWebServer.cpp
+++ b/src/network/CrossPointWebServer.cpp
@@ -11,6 +11,7 @@
 
 #include "html/FilesPageHtml.generated.h"
 #include "html/HomePageHtml.generated.h"
+#include "util/StringUtils.h"
 
 namespace {
 // Folders/files to hide from the web interface file browser
@@ -33,9 +34,8 @@ bool wsUploadInProgress = false;
 // Helper function to clear epub cache after upload
 void clearEpubCacheIfNeeded(const String& filePath) {
   // Only clear cache for .epub files
-  if (filePath.endsWith(".epub") || filePath.endsWith(".EPUB")) {
-    Epub epub(filePath.c_str(), "/.crosspoint");
-    epub.clearCache();
+  if (StringUtils::checkFileExtension(filePath, ".epub")) {
+    Epub(filePath.c_str(), "/.crosspoint").clearCache();
     Serial.printf("[%lu] [WEB] Cleared epub cache for: %s\n", millis(), filePath.c_str());
   }
 }
diff --git a/src/util/StringUtils.cpp b/src/util/StringUtils.cpp
index e56bc9d..1c5c499 100644
--- a/src/util/StringUtils.cpp
+++ b/src/util/StringUtils.cpp
@@ -49,6 +49,19 @@ bool checkFileExtension(const std::string& fileName, const char* extension) {
   return true;
 }
 
+bool checkFileExtension(const String& fileName, const char* extension) {
+  if (fileName.length() < strlen(extension)) {
+    return false;
+  }
+
+  String localFile(fileName);
+  String localExtension(extension);
+  localFile.toLowerCase();
+  localExtension.toLowerCase();
+  return localFile.endsWith(localExtension);
+}
+
+
 size_t utf8RemoveLastChar(std::string& str) {
   if (str.empty()) return 0;
   size_t pos = str.size() - 1;
diff --git a/src/util/StringUtils.h b/src/util/StringUtils.h
index e001d7b..8d75125 100644
--- a/src/util/StringUtils.h
+++ b/src/util/StringUtils.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <string>
+#include <WString.h>
 
 namespace StringUtils {
 
@@ -15,6 +16,7 @@ std::string sanitizeFilename(const std::string& name, size_t maxLength = 100);
  * Check if the given filename ends with the specified extension (case-insensitive).
  */
 bool checkFileExtension(const std::string& fileName, const char* extension);
+bool checkFileExtension(const String& fileName, const char* extension);
 
 // UTF-8 safe string truncation - removes one character from the end
 // Returns the new size after removing one UTF-8 character