Index: lib/Support/Windows/Process.inc
===================================================================
--- lib/Support/Windows/Process.inc
+++ lib/Support/Windows/Process.inc
@@ -417,16 +417,23 @@
   return 0;
 }
 
+// Include GetLastError() in a fatal error message.
+static void ReportLastErrorFatal(const char *msg) {
+  std::string ErrMsg;
+  MakeErrMsg(&ErrMsg, msg);
+  report_fatal_error(ErrMsg);
+}
+
 unsigned Process::GetRandomNumber() {
   HCRYPTPROV HCPC;
   if (!::CryptAcquireContextW(&HCPC, NULL, NULL, PROV_RSA_FULL,
                               CRYPT_VERIFYCONTEXT))
-    report_fatal_error("Could not acquire a cryptographic context");
+    ReportLastErrorFatal("Could not acquire a cryptographic context");
 
   ScopedCryptContext CryptoProvider(HCPC);
   unsigned Ret;
   if (!::CryptGenRandom(CryptoProvider, sizeof(Ret),
                         reinterpret_cast<BYTE *>(&Ret)))
-    report_fatal_error("Could not generate a random number");
+    ReportLastErrorFatal("Could not generate a random number");
   return Ret;
 }