diff --git a/configure.py b/configure.py
index 850bb98..0393cdd 100755
--- a/configure.py
+++ b/configure.py
@@ -351,7 +351,7 @@
     except:
         pass
     if platform.is_mingw():
-        cflags += ['-D_WIN32_WINNT=0x0501']
+        cflags += ['-D_WIN32_WINNT=0x0601']
     ldflags = ['-L$builddir']
     if platform.uses_usr_local():
         cflags.append('-I/usr/local/include')
diff --git a/src/util.cc b/src/util.cc
index ee810d6..f80616b 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -481,9 +481,7 @@
 
 int GetProcessorCount() {
 #ifdef _WIN32
-  SYSTEM_INFO info;
-  GetNativeSystemInfo(&info);
-  return info.dwNumberOfProcessors;
+  return GetActiveProcessorCount(ALL_PROCESSOR_GROUPS);
 #else
 #ifdef CPU_COUNT
   // The number of exposed processors might not represent the actual number of