diff --git a/src/main/scala/viper/gobra/util/TypeBounds.scala b/src/main/scala/viper/gobra/util/TypeBounds.scala
index 2682ce845..77712ca04 100644
--- a/src/main/scala/viper/gobra/util/TypeBounds.scala
+++ b/src/main/scala/viper/gobra/util/TypeBounds.scala
@@ -43,8 +43,8 @@ object TypeBounds {
   }
 
   sealed trait Signed extends BoundedIntegerKind {
-    override lazy val upper: BigInt = BigInt(pow(2, nbits-1).toLong - 1)
-    override lazy val lower: BigInt = BigInt(-pow(2, nbits-1).toLong)
+    override lazy val upper: BigInt = BigInt(pow(2, nbits-1).toLong)
+    override lazy val lower: BigInt = BigInt(-pow(2, nbits-1).toLong-1)
   }
 
   sealed trait Unsigned extends BoundedIntegerKind {