diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 9d3dcc44..4bc6ed1a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -198,7 +198,7 @@ build_mac:
         -DUSE_NATIVE_ARCH=OFF
         -DUSE_CCACHE=ON
         -DENABLE_UNIT_TESTS=ON
-        -DCMAKE_OSX_DEPLOYMENT_TARGET=10.9
+        -DCMAKE_OSX_DEPLOYMENT_TARGET=10.12
         -DCMAKE_OSX_SYSROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk
     - make -j5 install
 
diff --git a/external_dependencies/pybind11 b/external_dependencies/pybind11
index 2a150736..b9387195 160000
--- a/external_dependencies/pybind11
+++ b/external_dependencies/pybind11
@@ -1 +1 @@
-Subproject commit 2a150736601bb3113877bb673fb934bb60d46ec5
+Subproject commit b9387195ef024f4b96f1cba68d30b0d5539e6bf9
diff --git a/libsrc/core/CMakeLists.txt b/libsrc/core/CMakeLists.txt
index 368247ed..15198d50 100644
--- a/libsrc/core/CMakeLists.txt
+++ b/libsrc/core/CMakeLists.txt
@@ -10,6 +10,11 @@ add_library(ngcore SHARED
   utils.cpp
   )
 
+# Pybind11 2.3 Issue https://github.com/pybind/pybind11/issues/1604
+if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+  target_compile_options(ngcore PUBLIC -fsized-deallocation -faligned-allocation)
+endif()
+
 if(USE_PYTHON)
   target_sources(ngcore PRIVATE python_ngcore.cpp)
 endif(USE_PYTHON)
diff --git a/libsrc/core/ngcore_api.hpp b/libsrc/core/ngcore_api.hpp
index dfdee659..4841eb07 100644
--- a/libsrc/core/ngcore_api.hpp
+++ b/libsrc/core/ngcore_api.hpp
@@ -73,6 +73,7 @@ inline void operator delete[]( void* ptr, std::align_val_t al ) noexcept
   else
     delete[] (char*)ptr;
 }
+
 #endif // __MAC_OS_X_VERSION_MIN_REQUIRED
 #endif // __MAC_OS_X_VERSION_MIN_REQUIRED < 101300
 
diff --git a/libsrc/core/python_ngcore.cpp b/libsrc/core/python_ngcore.cpp
index f60e40d3..5e64d1b2 100644
--- a/libsrc/core/python_ngcore.cpp
+++ b/libsrc/core/python_ngcore.cpp
@@ -1,10 +1,6 @@
-#include <pybind11/pybind11.h>
 
-#include "python_ngcore.hpp"
-
-#include "array.hpp"
-#include "flags.hpp"
 #include "logging.hpp"
+#include "python_ngcore.hpp"
 
 namespace py = pybind11;
 using std::string;
diff --git a/libsrc/core/python_ngcore.hpp b/libsrc/core/python_ngcore.hpp
index 7b22ee79..1a071dc2 100644
--- a/libsrc/core/python_ngcore.hpp
+++ b/libsrc/core/python_ngcore.hpp
@@ -1,6 +1,7 @@
 #ifndef NETGEN_CORE_PYTHON_NGCORE_HPP
 #define NETGEN_CORE_PYTHON_NGCORE_HPP
 
+#include "ngcore_api.hpp" // for operator new
 #include <pybind11/pybind11.h>
 
 #include "array.hpp"
diff --git a/libsrc/general/ngpython.hpp b/libsrc/general/ngpython.hpp
index e13533c1..ef02d19f 100644
--- a/libsrc/general/ngpython.hpp
+++ b/libsrc/general/ngpython.hpp
@@ -1,13 +1,13 @@
 #ifdef NG_PYTHON
 
-#include <pybind11/pybind11.h>
+#include <core/python_ngcore.hpp>
+
 #include <pybind11/operators.h>
 #include <pybind11/numpy.h>
 #include <pybind11/stl.h>
 #include <iostream>
 #include <sstream>
 
-#include <core/python_ngcore.hpp>
 using namespace ngcore;
 
 template <typename T>
diff --git a/libsrc/meshing/python_mesh.hpp b/libsrc/meshing/python_mesh.hpp
index 62a85778..cc554fc6 100644
--- a/libsrc/meshing/python_mesh.hpp
+++ b/libsrc/meshing/python_mesh.hpp
@@ -1,9 +1,8 @@
 #ifndef NETGEN_MESHING_PYTHON_MESH_HPP
 #define NETGEN_MESHING_PYTHON_MESH_HPP
 
-#include <pybind11/pybind11.h>
-
 #include <core/python_ngcore.hpp>
+
 #include "meshing.hpp"
 
 namespace netgen