diff --git a/src/libromdata/disc/CisoPspDlopen.cpp b/src/libromdata/disc/CisoPspDlopen.cpp
index ef80bdc71..6d7d5cd4d 100644
--- a/src/libromdata/disc/CisoPspDlopen.cpp
+++ b/src/libromdata/disc/CisoPspDlopen.cpp
@@ -14,6 +14,7 @@
 #ifdef _WIN32
 #  include "libwin32common/RpWin32_sdk.h"
 #  define sched_yield() SwitchToThread()
+static constexpr pthread_once_t PTHREAD_ONCE_INIT = 0;
 #endif
 
 #ifdef _MSC_VER