diff --git a/opm/core/fluid/RockCompressibility.cpp b/opm/core/fluid/RockCompressibility.cpp
index dac8c37ce..7ca7acfb3 100644
--- a/opm/core/fluid/RockCompressibility.cpp
+++ b/opm/core/fluid/RockCompressibility.cpp
@@ -57,6 +57,11 @@ namespace Opm
         }
     }
 
+    bool RockCompressibility::isActive() const
+    {
+        return p_.empty() && (rock_comp_ == 0.0);
+    }
+
     double RockCompressibility::poroMult(double pressure)
     {
         if (p_.empty()) {
diff --git a/opm/core/fluid/RockCompressibility.hpp b/opm/core/fluid/RockCompressibility.hpp
index 5ae1a9ba4..94220d318 100644
--- a/opm/core/fluid/RockCompressibility.hpp
+++ b/opm/core/fluid/RockCompressibility.hpp
@@ -32,6 +32,7 @@ namespace Opm
     {
     public:
         /// Construct from input deck.
+        /// Looks for the keywords ROCK and ROCKTAB.
         RockCompressibility(const EclipseGridParser& deck);
 
         /// Construct from parameters.
@@ -40,6 +41,9 @@ namespace Opm
         ///    rock_compressibility      (0.0)     [given in bar^{-1}]
         RockCompressibility(const parameter::ParameterGroup& param);
 
+        /// Returns true if there are compressibility effects.
+        bool isActive() const;
+
         /// Porosity multiplier.
         double poroMult(double pressure);