diff --git a/dumux/material/fluidsystems/1p.hh b/dumux/material/fluidsystems/1p.hh
index a476c59b9d836486b1592722945f48a61bfd532a..599e4a9d353b50dfbab6e8d1c38c2dcc712d61f1 100644
--- a/dumux/material/fluidsystems/1p.hh
+++ b/dumux/material/fluidsystems/1p.hh
@@ -24,9 +24,12 @@
 #ifndef DUMUX_1P_FLUIDSYSTEM_HH
 #define DUMUX_1P_FLUIDSYSTEM_HH
 
+#warning "This header is deprecated! Use LiquidPhase (liquidphase.hh) or GasPhase (gasphase.hh) directly"
+
 #include <limits>
 #include <cassert>
 
+#include <dune/common/deprecated.hh>
 #include <dune/common/exceptions.hh>
 #include "base.hh"
 
@@ -44,7 +47,7 @@ namespace FluidSystems {
  * FluidSystems::GasPhase<Component> may be used.
  */
 template <class Scalar, class FluidType>
-class OneP
+class DUNE_DEPRECATED_MSG("OneP fluid system is deprecated! Use LiquidPhase or GasPhase directly") OneP
     : public BaseFluidSystem<Scalar, OneP<Scalar, FluidType> >
 {
     using ThisType = OneP<Scalar, FluidType>;