diff --git a/dune/tectonic/samplefunctional.hh b/dune/tectonic/samplefunctional.hh
index 1592c2922159642b2db7c9707e6e12d8a34b261d..4197cf6cde52370f021d34f84b2282f101c4e077 100644
--- a/dune/tectonic/samplefunctional.hh
+++ b/dune/tectonic/samplefunctional.hh
@@ -137,7 +137,7 @@ void minimise(Functional const J, typename Functional::SmallVector &x,
 
   for (size_t step = 0; step < steps; ++step) {
     SmallVector descDir;
-    double linesearchp = J.descentDirection(x, descDir);
+    bool const linesearchp = J.descentDirection(x, descDir);
 
     if (descDir == SmallVector(0.0))
       return;