diff --git a/torba/tests/client_tests/unit/test_headers.py b/torba/tests/client_tests/unit/test_headers.py
index c0efa0624..d99755679 100644
--- a/torba/tests/client_tests/unit/test_headers.py
+++ b/torba/tests/client_tests/unit/test_headers.py
@@ -94,6 +94,17 @@ class BasicHeadersTests(BitcoinHeadersTestCase):
         await headers.connect(len(headers), remainder)
         self.assertEqual(headers.height, 32259)
 
+    async def test_bounds(self):
+        headers = MainHeaders(':memory:')
+        await headers.connect(0, self.get_bytes(block_bytes(3001)))
+        self.assertEqual(headers.height, 3000)
+        with self.assertRaises(IndexError):
+            _ = headers[3001]
+        with self.assertRaises(IndexError):
+            _ = headers[-1]
+        self.assertIsNotNone(headers[3000])
+        self.assertIsNotNone(headers[0])
+
     async def test_repair(self):
         headers = MainHeaders(':memory:')
         await headers.connect(0, self.get_bytes(block_bytes(3001)))
diff --git a/torba/torba/client/baseheader.py b/torba/torba/client/baseheader.py
index c48fbdb9f..1df30ba10 100644
--- a/torba/torba/client/baseheader.py
+++ b/torba/torba/client/baseheader.py
@@ -70,8 +70,10 @@ class BaseHeaders:
         return True
 
     def __getitem__(self, height) -> dict:
-        assert not isinstance(height, slice), \
-            "Slicing of header chain has not been implemented yet."
+        if isinstance(height, slice):
+            raise NotImplementedError("Slicing of header chain has not been implemented yet.")
+        if not 0 <= height <= self.height:
+            raise IndexError(f"{height} is out of bounds, current height: {self.height}")
         return self.deserialize(height, self.get_raw_header(height))
 
     def get_raw_header(self, height) -> bytes: