diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
index 0ef6df0ff0..3fefb612bd 100644
--- a/lib/vtls/mbedtls.c
+++ b/lib/vtls/mbedtls.c
@@ -110,7 +110,8 @@ struct mbed_ssl_backend_data {
 };
 
 /* apply threading? */
-#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
+#if (defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)) || \
+    defined(_WIN32)
 #define THREADING_SUPPORT
 #endif
 
@@ -123,7 +124,6 @@ static mbedtls_entropy_context ts_entropy;
 
 static int entropy_init_initialized = 0;
 
-/* start of entropy_init_mutex() */
 static void entropy_init_mutex(mbedtls_entropy_context *ctx)
 {
   /* lock 0 = entropy_init_mutex() */
@@ -134,9 +134,18 @@ static void entropy_init_mutex(mbedtls_entropy_context *ctx)
   }
   Curl_mbedtlsthreadlock_unlock_function(0);
 }
-/* end of entropy_init_mutex() */
 
-/* start of entropy_func_mutex() */
+static void entropy_cleanup_mutex(mbedtls_entropy_context *ctx)
+{
+  /* lock 0 = use same lock as init */
+  Curl_mbedtlsthreadlock_lock_function(0);
+  if(entropy_init_initialized == 1) {
+    mbedtls_entropy_free(ctx);
+    entropy_init_initialized = 0;
+  }
+  Curl_mbedtlsthreadlock_unlock_function(0);
+}
+
 static int entropy_func_mutex(void *data, unsigned char *output, size_t len)
 {
   int ret;
@@ -147,7 +156,6 @@ static int entropy_func_mutex(void *data, unsigned char *output, size_t len)
 
   return ret;
 }
-/* end of entropy_func_mutex() */
 
 #endif /* THREADING_SUPPORT */
 
@@ -377,7 +385,6 @@ mbed_connect_step1(struct Curl_cfilter *cf, struct Curl_easy *data)
   }
 
 #ifdef THREADING_SUPPORT
-  entropy_init_mutex(&ts_entropy);
   mbedtls_ctr_drbg_init(&backend->ctr_drbg);
 
   ret = mbedtls_ctr_drbg_seed(&backend->ctr_drbg, entropy_func_mutex,
@@ -1246,14 +1253,19 @@ static CURLcode mbedtls_connect(struct Curl_cfilter *cf,
  */
 static int mbedtls_init(void)
 {
-  return Curl_mbedtlsthreadlock_thread_setup();
+  if(!Curl_mbedtlsthreadlock_thread_setup())
+    return 0;
+#ifdef THREADING_SUPPORT
+  entropy_init_mutex(&ts_entropy);
+#endif
+  return 1;
 }
 
 static void mbedtls_cleanup(void)
 {
 #ifdef THREADING_SUPPORT
-  mbedtls_entropy_free(&ts_entropy);
-#endif /* THREADING_SUPPORT */
+  entropy_cleanup_mutex(&ts_entropy);
+#endif
   (void)Curl_mbedtlsthreadlock_thread_cleanup();
 }
 
diff --git a/lib/vtls/mbedtls_threadlock.c b/lib/vtls/mbedtls_threadlock.c
index 22b1b221e7..b96a904fcb 100644
--- a/lib/vtls/mbedtls_threadlock.c
+++ b/lib/vtls/mbedtls_threadlock.c
@@ -26,12 +26,12 @@
 
 #if defined(USE_MBEDTLS) &&                                     \
   ((defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)) ||   \
-    defined(USE_THREADS_WIN32))
+    defined(_WIN32))
 
 #if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
 #  include <pthread.h>
 #  define MBEDTLS_MUTEX_T pthread_mutex_t
-#elif defined(USE_THREADS_WIN32)
+#elif defined(_WIN32)
 #  define MBEDTLS_MUTEX_T HANDLE
 #endif
 
@@ -59,7 +59,7 @@ int Curl_mbedtlsthreadlock_thread_setup(void)
 #if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
     if(pthread_mutex_init(&mutex_buf[i], NULL))
       return 0; /* pthread_mutex_init failed */
-#elif defined(USE_THREADS_WIN32)
+#elif defined(_WIN32)
     mutex_buf[i] = CreateMutex(0, FALSE, 0);
     if(mutex_buf[i] == 0)
       return 0;  /* CreateMutex failed */
@@ -80,7 +80,7 @@ int Curl_mbedtlsthreadlock_thread_cleanup(void)
 #if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
     if(pthread_mutex_destroy(&mutex_buf[i]))
       return 0; /* pthread_mutex_destroy failed */
-#elif defined(USE_THREADS_WIN32)
+#elif defined(_WIN32)
     if(!CloseHandle(mutex_buf[i]))
       return 0; /* CloseHandle failed */
 #endif /* USE_THREADS_POSIX && HAVE_PTHREAD_H */
@@ -100,7 +100,7 @@ int Curl_mbedtlsthreadlock_lock_function(int n)
                      "Error: mbedtlsthreadlock_lock_function failed\n"));
       return 0; /* pthread_mutex_lock failed */
     }
-#elif defined(USE_THREADS_WIN32)
+#elif defined(_WIN32)
     if(WaitForSingleObject(mutex_buf[n], INFINITE) == WAIT_FAILED) {
       DEBUGF(fprintf(stderr,
                      "Error: mbedtlsthreadlock_lock_function failed\n"));
@@ -120,7 +120,7 @@ int Curl_mbedtlsthreadlock_unlock_function(int n)
                      "Error: mbedtlsthreadlock_unlock_function failed\n"));
       return 0; /* pthread_mutex_unlock failed */
     }
-#elif defined(USE_THREADS_WIN32)
+#elif defined(_WIN32)
     if(!ReleaseMutex(mutex_buf[n])) {
       DEBUGF(fprintf(stderr,
                      "Error: mbedtlsthreadlock_unlock_function failed\n"));
diff --git a/lib/vtls/mbedtls_threadlock.h b/lib/vtls/mbedtls_threadlock.h
index 2b0bd41c8b..c8557e723e 100644
--- a/lib/vtls/mbedtls_threadlock.h
+++ b/lib/vtls/mbedtls_threadlock.h
@@ -29,7 +29,7 @@
 #ifdef USE_MBEDTLS
 
 #if (defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)) || \
-     defined(USE_THREADS_WIN32)
+    defined(_WIN32)
 
 int Curl_mbedtlsthreadlock_thread_setup(void);
 int Curl_mbedtlsthreadlock_thread_cleanup(void);