diff --git a/pygds/reader.py b/pygds/reader.py
index af5349b..2f591ba 100644
--- a/pygds/reader.py
+++ b/pygds/reader.py
@@ -90,7 +90,7 @@ class Reader(ProgressGetter):
                 result *= 16**exp
 
                 if int(temp[0]) & 0x80:
-                    result += -1
+                    result *= -1
 
                 return result