diff --git a/src/test/perf/external_pointer/externalpointer.cc b/src/test/perf/external_pointer/externalpointer.cc
index d4124b3..f6a8478 100644
--- a/src/test/perf/external_pointer/externalpointer.cc
+++ b/src/test/perf/external_pointer/externalpointer.cc
@@ -54,7 +54,13 @@ namespace test
 #ifdef NDEBUG
     static constexpr size_t iterations = 10000000;
 #else
+#  ifdef _MSC_VER
+    // Windows Debug build is very slow on this test.
+    // Reduce complexity to balance CI times.
+    static constexpr size_t iterations = 50000;
+#  else
     static constexpr size_t iterations = 100000;
+#  endif
 #endif
     setup(r, alloc);