diff --git a/lib/vtls/polarssl_threadlock.c b/lib/vtls/polarssl_threadlock.c
index dd5fbd7ec..8ef651d40 100644
--- a/lib/vtls/polarssl_threadlock.c
+++ b/lib/vtls/polarssl_threadlock.c
@@ -23,16 +23,15 @@
 #include "curl_setup.h"
 
 #if (defined(USE_POLARSSL) || defined(USE_MBEDTLS)) && \
-    (defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32))
+    ((defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)) || \
+     (defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H)))
 
-#if defined(USE_THREADS_POSIX)
-#  ifdef HAVE_PTHREAD_H
-#    include <pthread.h>
-#  endif
-#elif defined(USE_THREADS_WIN32)
-#  ifdef HAVE_PROCESS_H
-#    include <process.h>
-#  endif
+#if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
+#  include <pthread.h>
+#  define POLARSSL_MUTEX_T pthread_mutex_t
+#elif defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H)
+#  include <process.h>
+#  define POLARSSL_MUTEX_T HANDLE
 #endif
 
 #include "polarssl_threadlock.h"
@@ -56,19 +55,19 @@ int Curl_polarsslthreadlock_thread_setup(void)
   if(!mutex_buf)
     return 0;     /* error, no number of threads defined */
 
-#ifdef HAVE_PTHREAD_H
+#if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
   for(i = 0;  i < NUMT;  i++) {
     ret = pthread_mutex_init(&mutex_buf[i], NULL);
     if(ret)
       return 0; /* pthread_mutex_init failed */
   }
-#elif defined(HAVE_PROCESS_H)
+#elif defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H)
   for(i = 0;  i < NUMT;  i++) {
     mutex_buf[i] = CreateMutex(0, FALSE, 0);
     if(mutex_buf[i] == 0)
       return 0;  /* CreateMutex failed */
   }
-#endif /* HAVE_PTHREAD_H */
+#endif /* USE_THREADS_POSIX && HAVE_PTHREAD_H */
 
   return 1; /* OK */
 }
@@ -81,19 +80,19 @@ int Curl_polarsslthreadlock_thread_cleanup(void)
   if(!mutex_buf)
     return 0; /* error, no threads locks defined */
 
-#ifdef HAVE_PTHREAD_H
+#if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
   for(i = 0; i < NUMT; i++) {
     ret = pthread_mutex_destroy(&mutex_buf[i]);
     if(ret)
       return 0; /* pthread_mutex_destroy failed */
   }
-#elif defined(HAVE_PROCESS_H)
+#elif defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H)
   for(i = 0; i < NUMT; i++) {
     ret = CloseHandle(mutex_buf[i]);
     if(!ret)
       return 0; /* CloseHandle failed */
   }
-#endif /* HAVE_PTHREAD_H */
+#endif /* USE_THREADS_POSIX && HAVE_PTHREAD_H */
   free(mutex_buf);
   mutex_buf = NULL;
 
@@ -103,7 +102,7 @@ int Curl_polarsslthreadlock_thread_cleanup(void)
 int Curl_polarsslthreadlock_lock_function(int n)
 {
   int ret;
-#ifdef HAVE_PTHREAD_H
+#if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
   if(n < NUMT) {
     ret = pthread_mutex_lock(&mutex_buf[n]);
     if(ret) {
@@ -112,7 +111,7 @@ int Curl_polarsslthreadlock_lock_function(int n)
       return 0; /* pthread_mutex_lock failed */
     }
   }
-#elif defined(HAVE_PROCESS_H)
+#elif defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H)
   if(n < NUMT) {
     ret = (WaitForSingleObject(mutex_buf[n], INFINITE) == WAIT_FAILED?1:0);
     if(ret) {
@@ -121,14 +120,14 @@ int Curl_polarsslthreadlock_lock_function(int n)
       return 0; /* pthread_mutex_lock failed */
     }
   }
-#endif /* HAVE_PTHREAD_H */
+#endif /* USE_THREADS_POSIX && HAVE_PTHREAD_H */
   return 1; /* OK */
 }
 
 int Curl_polarsslthreadlock_unlock_function(int n)
 {
   int ret;
-#ifdef HAVE_PTHREAD_H
+#if defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)
   if(n < NUMT) {
     ret = pthread_mutex_unlock(&mutex_buf[n]);
     if(ret) {
@@ -137,7 +136,7 @@ int Curl_polarsslthreadlock_unlock_function(int n)
       return 0; /* pthread_mutex_unlock failed */
     }
   }
-#elif defined(HAVE_PROCESS_H)
+#elif defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H)
   if(n < NUMT) {
     ret = ReleaseMutex(mutex_buf[n]);
     if(!ret) {
@@ -146,7 +145,7 @@ int Curl_polarsslthreadlock_unlock_function(int n)
       return 0; /* pthread_mutex_lock failed */
     }
   }
-#endif /* HAVE_PTHREAD_H */
+#endif /* USE_THREADS_POSIX && HAVE_PTHREAD_H */
   return 1; /* OK */
 }
 
diff --git a/lib/vtls/polarssl_threadlock.h b/lib/vtls/polarssl_threadlock.h
index dda5359b8..122647528 100644
--- a/lib/vtls/polarssl_threadlock.h
+++ b/lib/vtls/polarssl_threadlock.h
@@ -26,13 +26,8 @@
 
 #if (defined USE_POLARSSL) || (defined USE_MBEDTLS)
 
-#if defined(USE_THREADS_POSIX)
-#  define POLARSSL_MUTEX_T       pthread_mutex_t
-#elif defined(USE_THREADS_WIN32)
-#  define POLARSSL_MUTEX_T       HANDLE
-#endif
-
-#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
+#if (defined(USE_THREADS_POSIX) && defined(HAVE_PTHREAD_H)) || \
+    (defined(USE_THREADS_WIN32) && defined(HAVE_PROCESS_H))
 
 int Curl_polarsslthreadlock_thread_setup(void);
 int Curl_polarsslthreadlock_thread_cleanup(void);