diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 383f80f88..0ee17b9bd 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -7,8 +7,8 @@ on:
     branches:
       - master
 jobs:
-  osx_10_15:
-    runs-on: macos-10.15
+  osx:
+    runs-on: macos-latest
     steps:
       - uses: actions/checkout@v2
       - name: Build
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2364363b4..3db6e6e71 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -286,6 +286,9 @@ set(PAGMO_SRC_FILES
     "${CMAKE_CURRENT_SOURCE_DIR}/src/detail/type_name.cpp"
 )
 
+set_property(SOURCE src/problems/cec2013.cpp
+             PROPERTY SKIP_UNITY_BUILD_INCLUSION ON)
+
 # Optional and platform-dependent bits.
 if(PAGMO_WITH_FORK_ISLAND)
     set(PAGMO_SRC_FILES
diff --git a/src/problems/wfg.cpp b/src/problems/wfg.cpp
index 77ebe66fc..4b7f6f022 100644
--- a/src/problems/wfg.cpp
+++ b/src/problems/wfg.cpp
@@ -916,10 +916,8 @@ vector_double wfg::wfg8_fitness(const vector_double &x) const
     for (decltype(m_dim_k) i = m_dim_k; i < m_dim_dvs; ++i) {
         vector_double first_input(i);
         vector_double weights(i, 1.0);
-        decltype(m_dim_obj) index = 0u;
         for (decltype(i) j = 0u; j < i; ++j) {
             first_input[j] = y[j];
-            ++index;
         }
         t_1[i] = b_param(x_norm[i], r_sum(first_input, weights), 0.98 / 49.98, 0.02, 50);
         y[i] = t_1[i];