Index: compiler-rt/lib/scudo/standalone/fuchsia.cpp
===================================================================
--- compiler-rt/lib/scudo/standalone/fuchsia.cpp
+++ compiler-rt/lib/scudo/standalone/fuchsia.cpp
@@ -88,6 +88,8 @@
   uintptr_t P;
   zx_vm_option_t MapFlags =
       ZX_VM_PERM_READ | ZX_VM_PERM_WRITE | ZX_VM_ALLOW_FAULTS;
+  if (Addr)
+    CHECK(Data);
   const uint64_t Offset =
       Addr ? reinterpret_cast<uintptr_t>(Addr) - Data->VmarBase : 0;
   if (Offset)