diff --git a/CMakeLists.txt b/CMakeLists.txt
index cd35af2..fb36210 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required (VERSION 3.15.7)
+cmake_minimum_required (VERSION 3.16.4)
 include(CheckFunctionExists)
 include(CheckSymbolExists)
 include(CheckLibraryExists)
diff --git a/appveyor.yml b/appveyor.yml
index 8ac2045..3d11467 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,25 +1,24 @@
 image:
-  - Visual Studio 2015
-  #- Visual Studio 2017
+  - Visual Studio 2019
 
 environment:
   PATH: C:\msys64\usr\bin;C:\msys64\mingw64\bin;C:\Windows\System32;C:\Windows;%PATH%
 
   matrix:
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      GENERATOR: Visual Studio 14 2015 Win64
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      GENERATOR: Visual Studio 16 2019 Win64
       CONFIG: Release
       SHARED_LIBS: ON
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      GENERATOR: Visual Studio 14 2015
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      GENERATOR: Visual Studio 16 2019
       CONFIG: Release
       SHARED_LIBS: ON
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      GENERATOR: Visual Studio 14 2015 Win64
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      GENERATOR: Visual Studio 16 2019 Win64
       CONFIG: Release
       SHARED_LIBS: OFF
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      GENERATOR: Visual Studio 14 2015
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      GENERATOR: Visual Studio 16 2019
       CONFIG: Release
       SHARED_LIBS: OFF