diff --git a/libcxx/src/random.cpp b/libcxx/src/random.cpp
--- a/libcxx/src/random.cpp
+++ b/libcxx/src/random.cpp
@@ -13,6 +13,7 @@
 #define _CRT_RAND_S
 #endif // defined(_LIBCPP_USING_WIN32_RANDOM)
 
+#include "limits"
 #include "random"
 #include "system_error"
 
@@ -33,7 +34,6 @@
 #include <nacl/nacl_random.h>
 #endif
 
-
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if defined(_LIBCPP_USING_GETENTROPY)
@@ -172,7 +172,11 @@
 double
 random_device::entropy() const _NOEXCEPT
 {
+#ifdef __OpenBSD__
+    return std::numeric_limits<unsigned int>::digits;
+#else
     return 0;
+#endif
 }
 
 _LIBCPP_END_NAMESPACE_STD