diff --git a/src/main/scala/vexriscv/plugin/PmpPlugin.scala b/src/main/scala/vexriscv/plugin/PmpPlugin.scala
index 1084891..54029d6 100644
--- a/src/main/scala/vexriscv/plugin/PmpPlugin.scala
+++ b/src/main/scala/vexriscv/plugin/PmpPlugin.scala
@@ -90,7 +90,7 @@ class PmpSetter(cutoff : Int) extends Component with Pmp {
 
   val ones = io.addr & ~(io.addr + 1)
   io.base := io.addr(xlen - 3 downto cutoff - 2) ^ ones(xlen - 3 downto cutoff - 2)
-  io.mask := ~ones(xlen - 2 downto cutoff - 1)
+  io.mask := ~(ones(xlen - 4 downto cutoff - 2) @@ U"1")
 }
 
 case class ProtectedMemoryTranslatorPort(bus : MemoryTranslatorBus)