diff --git a/dumux/implicit/fluxvariablesvector.hh b/dumux/implicit/fluxvariablesvector.hh
index 9745a5e1c4d4bfd867ecb2a28e1a8fc5b52aef43..b371bd7f605e4f87297399f0fe9e22c0b37d6769 100644
--- a/dumux/implicit/fluxvariablesvector.hh
+++ b/dumux/implicit/fluxvariablesvector.hh
@@ -59,7 +59,7 @@ public:
         return fluxVars_[scvfIdx];
     }
 
-    FluxVariables & operator [](IndexType scvfIdx)
+    FluxVariables& operator [](IndexType scvfIdx)
     {
         return fluxVars_[scvfIdx];
     }