diff --git a/WebVersion/main.js b/WebVersion/main.js
index 682501b..ca19e4f 100644
--- a/WebVersion/main.js
+++ b/WebVersion/main.js
@@ -32,12 +32,12 @@ function patch(view, fileNumber) {
     var version = readString(view.buffer, 0x00, 0x06);
     var validVersions = ["G8MJ01" /* JP */, "G8ME01" /* US */, "G8MP01" /* EU */];
     if (!validVersions.includes(version))
-        return 1 /* InvalidSaveFile */;
+        return 2 /* WrongSaveFileGameID */;
     var internalFilename = readString(view.buffer, 0x08, 0x11);
     if (internalFilename !== 'mariost_save_file')
-        return 1 /* InvalidSaveFile */;
+        return 3 /* WrongSaveFileInternalName */;
     if (fileNumber < 1 || fileNumber > 4)
-        return 2 /* InvalidFileNumber */;
+        return 4 /* InvalidFileNumber */;
     var offsetFile0 = ((fileNumber - 1) * 0x4000) + 0x2040;
     var offsetFile1 = offsetFile0 + 0x10000;
     function patchFilesU16(offset, value) {
@@ -122,11 +122,19 @@ function displayResult(e) {
         errorMessage.textContent = '';
         return true;
     }
-    else if (e === 1 /* InvalidSaveFile */) {
+    else if (e === 1 /* NotSaveFile */) {
         errorMessage.textContent = 'The file you specified was not a valid .gci save file';
         return false;
     }
-    else if (e === 2 /* InvalidFileNumber */) {
+    else if (e === 2 /* WrongSaveFileGameID */) {
+        errorMessage.textContent = 'This save file is not for Paper Mario: The Thousand Year Door';
+        return false;
+    }
+    else if (e === 3 /* WrongSaveFileInternalName */) {
+        errorMessage.textContent = 'This save file has the wrong internal ID. Please make sure you are using a normal Paper Mario: The Thousand Year Door save file.';
+        return false;
+    }
+    else if (e === 4 /* InvalidFileNumber */) {
         // should not happen
         throw "whoops";
     }
@@ -135,7 +143,7 @@ function fileSubmitted() {
     var input = document.querySelector('input#fileupload');
     var file = input.files[0];
     if (!file.name.endsWith('.gci')) {
-        if (!displayResult(1 /* InvalidSaveFile */))
+        if (!displayResult(1 /* NotSaveFile */))
             return;
     }
     var fileNumberInput = document.querySelector('select#filenumber');
diff --git a/WebVersion/main.ts b/WebVersion/main.ts
index 63f7d5a..915d455 100644
--- a/WebVersion/main.ts
+++ b/WebVersion/main.ts
@@ -42,7 +42,9 @@ function decodeBinaryData(S: string): ArrayBuffer {
 
 const enum PatchErrorCode {
     Success,
-    InvalidSaveFile,
+    NotSaveFile,
+    WrongSaveFileGameID,
+    WrongSaveFileInternalName,
     InvalidFileNumber,
 }
 
@@ -51,11 +53,11 @@ function patch(view: DataView, fileNumber: number): PatchErrorCode {
 
     const validVersions = [GameVersion.JP, GameVersion.US, GameVersion.EU];
     if (!validVersions.includes(version))
-        return PatchErrorCode.InvalidSaveFile;
+        return PatchErrorCode.WrongSaveFileGameID;
 
     const internalFilename = readString(view.buffer, 0x08, 0x11);
     if (internalFilename !== 'mariost_save_file')
-        return PatchErrorCode.InvalidSaveFile;
+        return PatchErrorCode.WrongSaveFileInternalName;
 
     if (fileNumber < 1 || fileNumber > 4)
         return PatchErrorCode.InvalidFileNumber;
@@ -153,9 +155,15 @@ function displayResult(e: PatchErrorCode): boolean {
     if (e === PatchErrorCode.Success) {
         errorMessage.textContent = '';
         return true;
-    } else if (e === PatchErrorCode.InvalidSaveFile) {
+    } else if (e === PatchErrorCode.NotSaveFile) {
         errorMessage.textContent = 'The file you specified was not a valid .gci save file';
         return false;
+    } else if (e === PatchErrorCode.WrongSaveFileGameID) {
+        errorMessage.textContent = 'This save file is not for Paper Mario: The Thousand Year Door';
+        return false;
+    } else if (e === PatchErrorCode.WrongSaveFileInternalName) {
+        errorMessage.textContent = 'This save file has the wrong internal ID. Please make sure you are using a normal Paper Mario: The Thousand Year Door save file.';
+        return false;
     } else if (e === PatchErrorCode.InvalidFileNumber) {
         // should not happen
         throw "whoops";
@@ -167,7 +175,7 @@ function fileSubmitted(): void {
     const file = input.files[0];
 
     if (!file.name.endsWith('.gci')) {
-        if (!displayResult(PatchErrorCode.InvalidSaveFile))
+        if (!displayResult(PatchErrorCode.NotSaveFile))
             return;
     }