diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 999efa1de..5a92a8e66 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -30,6 +30,15 @@ if("${CMAKE_LIBRARY_OUTPUT_DIRECTORY}" STREQUAL "")
     endif(MSVC OR CMAKE_GENERATOR STREQUAL "Xcode")
 endif("${CMAKE_LIBRARY_OUTPUT_DIRECTORY}" STREQUAL "")
 
+# enable global link time optimization
+cmake_policy(SET CMP0069 NEW)
+set(CMAKE_POLICY_DEFAULT_CMP0069 NEW)
+include(CheckIPOSupported)
+check_ipo_supported(RESULT ipo_supported OUTPUT ipo_supported_output)
+if(ipo_supported)
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+endif()
+
 include_directories(${pybind11_INCLUDE_DIR} ${PYTHON_INCLUDE_DIRS})
 pybind11_add_module(pyncnn src/main.cpp)
 set_target_properties(pyncnn PROPERTIES OUTPUT_NAME "ncnn")
diff --git a/python/pybind11 b/python/pybind11
index 80dc998ef..3e9dfa286 160000
--- a/python/pybind11
+++ b/python/pybind11
@@ -1 +1 @@
-Subproject commit 80dc998efced8ceb2be59756668a7e90e8bef917
+Subproject commit 3e9dfa2866941655c56877882565e7577de6fc7b
diff --git a/python/tests/test_mat.py b/python/tests/test_mat.py
index 7019961a5..205053ee5 100644
--- a/python/tests/test_mat.py
+++ b/python/tests/test_mat.py
@@ -298,7 +298,7 @@ def test_fill():
     mat = ncnn.Mat(1)
     mat.fill(1.0)
     array = np.array(mat)
-    assert np.abs(array[0] - 1.0) < sys.float_info.min
+    assert np.abs(array[0] - 1.0) < np.finfo(np.float32).eps
 
 
 def test_clone():