diff --git a/.github/ci/packages.apt b/.github/ci/packages.apt
index 8c85a08a1b..77df164d6e 100644
--- a/.github/ci/packages.apt
+++ b/.github/ci/packages.apt
@@ -23,6 +23,7 @@ libsdformat14-dev
 libtinyxml2-dev
 libxi-dev
 libxmu-dev
+libpython3-dev
 python3-distutils
 python3-gz-math7
 python3-gz-msgs10
diff --git a/src/SimulationRunner.cc b/src/SimulationRunner.cc
index 4f628a3906..4ee08be76a 100644
--- a/src/SimulationRunner.cc
+++ b/src/SimulationRunner.cc
@@ -80,6 +80,9 @@ struct MaybeGilScopedRelease
 #else
   struct MaybeGilScopedRelease
   {
+    // The empty constructor is needed to avoid an "unused variable" warning
+    // when an instance of this class is used.
+    MaybeGilScopedRelease(){}
   };
 #endif
 }