diff --git a/compiler-rt/lib/asan/asan_win.cpp b/compiler-rt/lib/asan/asan_win.cpp
--- a/compiler-rt/lib/asan/asan_win.cpp
+++ b/compiler-rt/lib/asan/asan_win.cpp
@@ -194,9 +194,12 @@
 }
 
 void FlushUnneededASanShadowMemory(uptr p, uptr size) {
+  // Only asan on 64-bit Windows supports committing shadow memory on demand.
+#if SANITIZER_WINDOWS64
   // Since asan's mapping is compacting, the shadow chunk may be
   // not page-aligned, so we only flush the page-aligned portion.
   ReleaseMemoryPagesToOS(MemToShadow(p), MemToShadow(p + size));
+#endif
 }
 
 // ---------------------- TSD ---------------- {{{