diff --git a/include/compat/pthread.h b/include/compat/pthread.h
index 861c8e1..8b8c3c6 100644
--- a/include/compat/pthread.h
+++ b/include/compat/pthread.h
@@ -3,6 +3,9 @@
  * pthread.h compatibility shim
  */
 
+#ifndef LIBCRYPTOCOMPAT_PTHREAD_H
+#define LIBCRYPTOCOMPAT_PTHREAD_H
+
 #ifdef _WIN32
 
 #include <windows.h>
@@ -52,6 +55,32 @@ pthread_equal(pthread_t t1, pthread_t t2)
 	return t1 == t2;
 }
 
+typedef CRITICAL_SECTION pthread_mutex_t;
+typedef void pthread_mutexattr_t;
+
+static inline int
+pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
+{
+	InitializeCriticalSection(mutex);
+	return 0;
+}
+
+static inline int
+pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+	EnterCriticalSection(mutex);
+	return 0;
+}
+
+static inline int
+pthread_mutex_unlock(pthread_mutex_t *mutex)
+{
+	LeaveCriticalSection(mutex);
+	return 0;
+}
+
 #else
 #include_next <pthread.h>
 #endif
+
+#endif