--- old/src/hotspot/os/windows/os_windows.cpp	2020-04-29 08:22:49.444183129 -0400
+++ new/src/hotspot/os/windows/os_windows.cpp	2020-04-29 08:22:49.136173198 -0400
@@ -4096,10 +4096,17 @@
     UseNUMA = false; // We don't fully support this yet
   }
 
-  if (UseNUMAInterleaving) {
-    // first check whether this Windows OS supports VirtualAllocExNuma, if not ignore this flag
-    bool success = numa_interleaving_init();
-    if (!success) UseNUMAInterleaving = false;
+  // If UseNUMA then UseNUMAInterleaving is later (Arguments) defaulted to
+  // true, but that's too late to call numa_interleaving_init.
+  if (UseNUMAInterleaving || (UseNUMA && FLAG_IS_DEFAULT(UseNUMAInterleaving))) {
+    // Check whether this Windows OS provides the needed support.
+    if (!numa_interleaving_init()) {
+      // Not supported, so disable flag and prevent later defaulted change.
+      FLAG_SET_ERGO(UseNUMAInterleaving, false);
+    } else if (!UseNUMAInterleaving) {
+      // Supported, so change flag now, rather than waiting for Arguments.
+      FLAG_SET_ERGO(UseNUMAInterleaving, true);
+    }
   }
 
   if (initSock() != JNI_OK) {