diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 5543c26a33ee0025832ff1d1ded3e695b20fcda1..fa6ec906cfbcd86499baae74c53ce78da970d592 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1052,9 +1052,9 @@ clang_6.0_hybrid:
    variables:
       <<: *build_hybrid_variables
       WALBERLA_BUILD_WITH_CUDA: "OFF"
-   except:
+   only:
       variables:
-         - $DISABLE_PER_COMMIT_BUILDS
+         - $ENABLE_NIGHTLY_BUILDS
    tags:
       - docker
 
@@ -1064,9 +1064,9 @@ clang_6.0_serial_dbg:
    variables:
       <<: *build_serial_dbg_variables
       WALBERLA_BUILD_WITH_CUDA: "OFF"
-   except:
+   only:
       variables:
-         - $DISABLE_PER_COMMIT_BUILDS
+         - $ENABLE_NIGHTLY_BUILDS
    tags:
       - docker
 
@@ -1076,9 +1076,9 @@ clang_6.0_mpionly_dbg:
    variables:
       <<: *build_mpionly_dbg_variables
       WALBERLA_BUILD_WITH_CUDA: "OFF"
-   except:
+   only:
       variables:
-         - $DISABLE_PER_COMMIT_BUILDS
+         - $ENABLE_NIGHTLY_BUILDS
    tags:
       - docker
 
@@ -1088,15 +1088,99 @@ clang_6.0_hybrid_dbg:
    variables:
       <<: *build_hybrid_dbg_variables
       WALBERLA_BUILD_WITH_CUDA: "OFF"
-   except:
+   only:
       variables:
-         - $DISABLE_PER_COMMIT_BUILDS
+         - $ENABLE_NIGHTLY_BUILDS
    tags:
       - docker
 
 clang_6.0_hybrid_dbg_sp:
    <<: *build_definition
    image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:6.0
+   variables:
+      <<: *build_hybrid_dbg_sp_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   only:
+      variables:
+         - $ENABLE_NIGHTLY_BUILDS
+   tags:
+      - docker
+
+clang_7.0_serial:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
+   variables:
+      <<: *build_serial_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   only:
+      variables:
+         - $ENABLE_NIGHTLY_BUILDS
+   tags:
+      - docker
+
+clang_7.0_mpionly:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
+   variables:
+      <<: *build_mpionly_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   only:
+      variables:
+         - $ENABLE_NIGHTLY_BUILDS
+   tags:
+      - docker
+
+clang_7.0_hybrid:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
+   variables:
+      <<: *build_hybrid_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   except:
+      variables:
+         - $DISABLE_PER_COMMIT_BUILDS
+   tags:
+      - docker
+
+clang_7.0_serial_dbg:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
+   variables:
+      <<: *build_serial_dbg_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   except:
+      variables:
+         - $DISABLE_PER_COMMIT_BUILDS
+   tags:
+      - docker
+
+clang_7.0_mpionly_dbg:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
+   variables:
+      <<: *build_mpionly_dbg_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   except:
+      variables:
+         - $DISABLE_PER_COMMIT_BUILDS
+   tags:
+      - docker
+
+clang_7.0_hybrid_dbg:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
+   variables:
+      <<: *build_hybrid_dbg_variables
+      WALBERLA_BUILD_WITH_CUDA: "OFF"
+   except:
+      variables:
+         - $DISABLE_PER_COMMIT_BUILDS
+   tags:
+      - docker
+
+clang_7.0_hybrid_dbg_sp:
+   <<: *build_definition
+   image: i10git.cs.fau.de:5005/walberla/buildenvs/clang:7.0
    variables:
       <<: *build_hybrid_dbg_sp_variables
       WALBERLA_BUILD_WITH_CUDA: "OFF"
diff --git a/src/field/python/FieldExport.impl.h b/src/field/python/FieldExport.impl.h
index a092b4103ecabc0882777e4e297be736cda3ef35..c8c2936a2b80b87a2ab48d3dcad25c5ef0832a66 100644
--- a/src/field/python/FieldExport.impl.h
+++ b/src/field/python/FieldExport.impl.h
@@ -686,7 +686,8 @@ namespace internal {
 
       for( auto i = flags.begin(); i != flags.end(); ++i )
          result.append( i->toString() );
-      return result;
+      boost::python::object objectResult = result;
+      return objectResult;
    }
 
 
@@ -699,7 +700,8 @@ namespace internal {
 
       for( auto i = flags.begin(); i != flags.end(); ++i )
          result[ i->toString() ] = ff.getFlag( *i );
-      return result;
+      boost::python::object objectResult = result;
+      return objectResult;
    }
 
    template<typename T>