diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6d5ed963..011c9052 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -61,6 +61,10 @@ IF (NOT PAHO_BUILD_SHARED AND NOT PAHO_BUILD_STATIC)
     MESSAGE(FATAL_ERROR "YOu must set either PAHO_BUILD_SHARED, PAHO_BUILD_STATIC, or both")
 ENDIF()
 
+IF (PAHO_BUILD_STATIC)
+  ADD_DEFINITIONS(-DPAHO_BUILD_STATIC=1)
+ENDIF()
+
 IF(PAHO_BUILD_DEB_PACKAGE)
     set(CMAKE_INSTALL_DOCDIR share/doc/libpaho-mqtt)
 ENDIF()
diff --git a/appveyor.yml b/appveyor.yml
index f5a42457..a5cb515e 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -12,7 +12,7 @@ environment:
       PENSSL_ROOT_DIR: "C:/OpenSSL-Win64"
       PAHO_BUILD_STATIC: FALSE
       PAHO_BUILD_SHARED: TRUE
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
       PAHO_WINDOWS_BUILD_BIT: x64
       PENSSL_ROOT_DIR: "C:/OpenSSL-Win64"
       PAHO_BUILD_STATIC: TRUE
@@ -39,6 +39,8 @@ build_script:
 
     echo %APPVEYOR_BUILD_WORKER_IMAGE%
 
+    if "%APPVEYOR_BUILD_WORKER_IMAGE%" == "Visual Studio 2019" call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat" %PAHO_WINDOWS_BUILD_BIT%
+
     if "%APPVEYOR_BUILD_WORKER_IMAGE%" == "Visual Studio 2015" call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" %PAHO_WINDOWS_BUILD_BIT%
 
     if "%APPVEYOR_BUILD_WORKER_IMAGE%" == "Visual Studio 2013" call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" %PAHO_WINDOWS_BUILD_BIT%
diff --git a/src/MQTTAsync.c b/src/MQTTAsync.c
index 99ff5a9e..5b85c902 100644
--- a/src/MQTTAsync.c
+++ b/src/MQTTAsync.c
@@ -117,30 +117,6 @@ extern mutex_type stack_mutex;
 extern mutex_type heap_mutex;
 extern mutex_type log_mutex;
 
-/*
-BOOL APIENTRY DllMain(HANDLE hModule,
-					  DWORD  ul_reason_for_call,
-					  LPVOID lpReserved)
-{
-	switch (ul_reason_for_call)
-	{
-		case DLL_PROCESS_ATTACH:
-			Log(TRACE_MAX, -1, "DLL process attach");
-			MQTTAsync_init();
-			break;
-		case DLL_THREAD_ATTACH:
-			Log(TRACE_MAX, -1, "DLL thread attach");
-			break;
-		case DLL_THREAD_DETACH:
-			Log(TRACE_MAX, -1, "DLL thread detach");
-			break;
-		case DLL_PROCESS_DETACH:
-			Log(TRACE_MAX, -1, "DLL process detach");
-		break;
-	}
-	return TRUE;
-}*/
-
 void MQTTAsync_init(void)
 {
 	if (mqttasync_mutex == NULL)
@@ -164,6 +140,7 @@ void MQTTAsync_init(void)
 	}
 }
 
+#if defined(PAHO_BUILD_STATIC)
 // Global variable for one-time initialization structure
 INIT_ONCE g_InitOnce = INIT_ONCE_STATIC_INIT; // Static initialization
 
@@ -205,6 +182,30 @@ BOOL CALLBACK InitHandleFunction (
 	MQTTAsync_init();
     return TRUE;
 }
+#else
+BOOL APIENTRY DllMain(HANDLE hModule,
+					  DWORD  ul_reason_for_call,
+					  LPVOID lpReserved)
+{
+	switch (ul_reason_for_call)
+	{
+		case DLL_PROCESS_ATTACH:
+			Log(TRACE_MAX, -1, "DLL process attach");
+			MQTTAsync_init();
+			break;
+		case DLL_THREAD_ATTACH:
+			Log(TRACE_MAX, -1, "DLL thread attach");
+			break;
+		case DLL_THREAD_DETACH:
+			Log(TRACE_MAX, -1, "DLL thread detach");
+			break;
+		case DLL_PROCESS_DETACH:
+			Log(TRACE_MAX, -1, "DLL process detach");
+		break;
+	}
+	return TRUE;
+}
+#endif
 
 
 #else
@@ -605,7 +606,7 @@ int MQTTAsync_createWithOptions(MQTTAsync* handle, const char* serverURI, const
 	int rc = 0;
 	MQTTAsyncs *m = NULL;
 
-#if defined(_WIN32) || defined(_WIN64)
+#if (defined(_WIN32) || defined(_WIN64)) && defined(PAHO_BUILD_STATIC)
 	OpenEventHandleSync(); /* intializes mutexes once.  Must come before FUNC_ENTRY */
 #endif
 	FUNC_ENTRY;
diff --git a/src/MQTTClient.c b/src/MQTTClient.c
index 504d4ad1..fe2d9049 100644
--- a/src/MQTTClient.c
+++ b/src/MQTTClient.c
@@ -112,30 +112,6 @@ extern mutex_type stack_mutex;
 extern mutex_type heap_mutex;
 extern mutex_type log_mutex;
 
-/*
-BOOL APIENTRY DllMain(HANDLE hModule,
-					  DWORD  ul_reason_for_call,
-					  LPVOID lpReserved)
-{
-	switch (ul_reason_for_call)
-	{
-		case DLL_PROCESS_ATTACH:
-			Log(TRACE_MAX, -1, "DLL process attach");
-			MQTTClient_init();
-			break;
-		case DLL_THREAD_ATTACH:
-			Log(TRACE_MAX, -1, "DLL thread attach");
-			break;
-		case DLL_THREAD_DETACH:
-			Log(TRACE_MAX, -1, "DLL thread detach");
-			break;
-		case DLL_PROCESS_DETACH:
-			Log(TRACE_MAX, -1, "DLL process detach");
-			break;
-	}
-	return TRUE;
-}*/
-
 void MQTTClient_init(void)
 {
 	if (mqttclient_mutex == NULL)
@@ -151,6 +127,7 @@ void MQTTClient_init(void)
 	}
 }
 
+#if defined(PAHO_BUILD_STATIC)
 // Global variable for one-time initialization structure
 INIT_ONCE g_InitOnce = INIT_ONCE_STATIC_INIT; // Static initialization
 
@@ -193,6 +170,30 @@ BOOL CALLBACK InitHandleFunction (
     return TRUE;
 }
 
+#else
+BOOL APIENTRY DllMain(HANDLE hModule,
+					  DWORD  ul_reason_for_call,
+					  LPVOID lpReserved)
+{
+	switch (ul_reason_for_call)
+	{
+		case DLL_PROCESS_ATTACH:
+			Log(TRACE_MAX, -1, "DLL process attach");
+			MQTTClient_init();
+			break;
+		case DLL_THREAD_ATTACH:
+			Log(TRACE_MAX, -1, "DLL thread attach");
+			break;
+		case DLL_THREAD_DETACH:
+			Log(TRACE_MAX, -1, "DLL thread detach");
+			break;
+		case DLL_PROCESS_DETACH:
+			Log(TRACE_MAX, -1, "DLL process detach");
+			break;
+	}
+	return TRUE;
+}
+#endif
 
 #else
 static pthread_mutex_t mqttclient_mutex_store = PTHREAD_MUTEX_INITIALIZER;
@@ -396,7 +397,7 @@ int MQTTClient_createWithOptions(MQTTClient* handle, const char* serverURI, cons
 	int rc = 0;
 	MQTTClients *m = NULL;
 
-#if defined(_WIN32) || defined(_WIN64)
+#if (defined(_WIN32) || defined(_WIN64)) && defined(PAHO_BUILD_STATIC)
 	OpenEventHandleSync(); /* intializes mutexes once.  Must come before FUNC_ENTRY */
 #endif
 	FUNC_ENTRY;