diff --git a/code/plastic_isotropic.f90 b/code/plastic_isotropic.f90
index da4198007..563952122 100644
--- a/code/plastic_isotropic.f90
+++ b/code/plastic_isotropic.f90
@@ -55,7 +55,7 @@ module plastic_isotropic
      tausat_SinhFitC, &
      tausat_SinhFitD
   logical :: &
-     dilatation
+     dilatation = .false.
  end type
 
  type(tParameters), dimension(:), allocatable, private :: param                                       !< containers of constitutive parameters (len Ninstance)