diff --git a/src/typedstream/stream.py b/src/typedstream/stream.py
index 2444db5..295ccfb 100644
--- a/src/typedstream/stream.py
+++ b/src/typedstream/stream.py
@@ -122,6 +122,8 @@
 _TAG_INTEGER_2 = -127
 # Indicates an integer value, stored in 4 bytes.
 _TAG_INTEGER_4 = -126
+# Indicates an integer value, stored in 8 bytes.
+_TAG_INTEGER_8 = -121
 # Indicates a floating-point value, stored in 4 or 8 bytes (depending on whether it is a float or a double).
 _TAG_FLOATING_POINT = -125
 # Indicates the start of a string value or an object that is stored literally and not as a backreference.
@@ -677,6 +679,8 @@ def _read_integer(self, head: typing.Optional[int] = None, *, signed: bool) -> i
 			return int.from_bytes(self._read_exact(2), self.byte_order, signed=signed)
 		elif head == _TAG_INTEGER_4:
 			return int.from_bytes(self._read_exact(4), self.byte_order, signed=signed)
+		elif head == _TAG_INTEGER_8:
+			return int.from_bytes(self._read_exact(8), self.byte_order, signed=signed)
 		else:
 			raise InvalidTypedStreamError(f"Invalid head tag in this context: {head} ({head & 0xff:#x})")