diff --git a/opm/polymer/PolymerProperties.cpp b/opm/polymer/PolymerProperties.cpp
index da5c86125..78fdd32da 100644
--- a/opm/polymer/PolymerProperties.cpp
+++ b/opm/polymer/PolymerProperties.cpp
@@ -59,13 +59,13 @@ namespace Opm
         return ads_index_;
     }
     
-    std::vector<double>
+    const std::vector<double>&
     PolymerProperties::shearWaterVelocity() const
     {
         return water_vel_vals_;
     } 
 
-    std::vector<double>
+    const std::vector<double>&
     PolymerProperties::shearVrf() const
     {
         return shear_vrf_vals_;
diff --git a/opm/polymer/PolymerProperties.hpp b/opm/polymer/PolymerProperties.hpp
index 79741bb1f..765c53c41 100644
--- a/opm/polymer/PolymerProperties.hpp
+++ b/opm/polymer/PolymerProperties.hpp
@@ -164,9 +164,9 @@ namespace Opm
 
         int adsIndex() const;
         
-        std::vector<double> shearWaterVelocity() const;
+        const std::vector<double>& shearWaterVelocity() const;
 
-        std::vector<double> shearVrf() const;
+        const std::vector<double>& shearVrf() const;
 
         double viscMult(double c) const;