diff --git a/libpyclingo/clingo/__init__.py b/libpyclingo/clingo/__init__.py
index f6b486289..805968675 100644
--- a/libpyclingo/clingo/__init__.py
+++ b/libpyclingo/clingo/__init__.py
@@ -82,7 +82,7 @@
 
     class Context:
         def inc(self, x):
-            return Number(x.number)
+            return Number(x.number + 1)
 
         def seq(self, x, y):
             return [x, y]