diff --git a/llvm/utils/lit/lit/util.py b/llvm/utils/lit/lit/util.py
index fb96b2238b891..0d8f0040f41cc 100644
--- a/llvm/utils/lit/lit/util.py
+++ b/llvm/utils/lit/lit/util.py
@@ -119,6 +119,12 @@ def usable_core_count():
         n = len(os.sched_getaffinity(0))
     except AttributeError:
         n = os.cpu_count() or 1
+
+    # On Windows, with more than 32 processes, process creation often fails with
+    # "Too many open files".  FIXME: Check if there's a better fix.
+    if platform.system() == 'Windows':
+        return min(n, 32)
+
     return n