diff --git a/stl/src/cthread.cpp b/stl/src/cthread.cpp
index 8f1c761cd5f..42a757f76f6 100644
--- a/stl/src/cthread.cpp
+++ b/stl/src/cthread.cpp
@@ -4,6 +4,7 @@
 // thread functions
 
 #include "awint.h"
+#include <bitset>
 #include <process.h>
 #include <stdint.h>
 #include <stdio.h>
@@ -99,9 +100,15 @@ _Thrd_id_t _Thrd_id() { // return unique id for current thread
 }
 
 unsigned int _Thrd_hardware_concurrency() { // return number of processors
-    SYSTEM_INFO info;
-    GetNativeSystemInfo(&info);
-    return info.dwNumberOfProcessors;
+    DWORD_PTR process_affinity_mask;
+    DWORD_PTR system_affinity_mask;
+    if (GetProcessAffinityMask(GetCurrentProcess(), &process_affinity_mask, &system_affinity_mask)) {
+        std::bitset<sizeof(DWORD_PTR) * CHAR_BIT> process_affinity_mask_bits(
+            static_cast<unsigned long long>(process_affinity_mask));
+        return static_cast<unsigned int>(process_affinity_mask_bits.count());
+    } else {
+        return 0;
+    }
 }
 
 // TRANSITION, ABI: _Thrd_create() is preserved for binary compatibility