diff --git a/compiler-rt/lib/asan/asan_poisoning.h b/compiler-rt/lib/asan/asan_poisoning.h
index d79190a6ef79972ea77d1cc63f76020752f154bc..63ac819513bd7ab3add856377acc0b032de429fa 100644
--- a/compiler-rt/lib/asan/asan_poisoning.h
+++ b/compiler-rt/lib/asan/asan_poisoning.h
@@ -39,7 +39,12 @@ ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
   uptr shadow_end = MEM_TO_SHADOW(
       aligned_beg + aligned_size - SHADOW_GRANULARITY) + 1;
+  // FIXME: Page states are different on Windows, so using the same interface
+  // for mapping shadow and zeroing out pages doesn't "just work", so we should
+  // probably provide higher-level interface for these operations.
+  // For now, just memset on Windows.
   if (value ||
+      SANITIZER_WINDOWS ||
       shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
     REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
   } else {