diff --git a/CHANGELOG.md b/CHANGELOG.md
index 789bfa9..46d857f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.1.1
+
+- Throw KdbxInvalidFileStructure for invalid files.
+
 ## 2.1.0
 
 - Implement permanently removing entries and groups.
diff --git a/lib/src/kdbx_header.dart b/lib/src/kdbx_header.dart
index 1b3d58f..889623b 100644
--- a/lib/src/kdbx_header.dart
+++ b/lib/src/kdbx_header.dart
@@ -385,7 +385,7 @@ class KdbxHeader {
     final sig1 = reader.readUint32();
     final sig2 = reader.readUint32();
     if (!(sig1 == Consts.FileMagic && sig2 == Consts.Sig2Kdbx)) {
-      throw UnsupportedError(
+      throw KdbxInvalidFileStructure(
           'Unsupported file structure. ${ByteUtils.toHex(sig1)}, '
           '${ByteUtils.toHex(sig2)}');
     }
@@ -583,6 +583,17 @@ class KdbxUnsupportedException implements KdbxException {
   }
 }
 
+class KdbxInvalidFileStructure implements KdbxException {
+  KdbxInvalidFileStructure(this.message);
+
+  final String message;
+
+  @override
+  String toString() {
+    return 'KdbxInvalidFileStructure{$message}';
+  }
+}
+
 class HashedBlockReader {
   static const BLOCK_SIZE = 1024 * 1024;
   static const HASH_SIZE = 32;