diff --git a/lib/Sema/TypeCheckConcurrency.cpp b/lib/Sema/TypeCheckConcurrency.cpp
index e293d91888a1a..52b2b9c4f749c 100644
--- a/lib/Sema/TypeCheckConcurrency.cpp
+++ b/lib/Sema/TypeCheckConcurrency.cpp
@@ -4113,7 +4113,8 @@ namespace {
       }
 
       if (auto *macro = dyn_cast<MacroExpansionExpr>(expr)) {
-        expr = macro->getRewritten();
+        if (auto rewritten = macro->getRewritten())
+          expr = rewritten;
       }
 
       if (auto *isolation = dyn_cast<CurrentContextIsolationExpr>(expr)) {