diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index ae95dd8..0c61496 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -3262,9 +3262,14 @@
 
     // If we have a null capture, this must be the C++ 'this' capture.
     if (!capture) {
-      const CXXMethodDecl *method =
-          cast<CXXMethodDecl>(blockDecl->getNonClosureContext());
-      QualType type = method->getThisType(C);
+      QualType type;
+      if (auto *Method =
+              cast_or_null<CXXMethodDecl>(blockDecl->getNonClosureContext()))
+        type = Method->getThisType(C);
+      else if (auto *RDecl = dyn_cast<CXXRecordDecl>(blockDecl->getParent()))
+        type = QualType(RDecl->getTypeForDecl(), 0);
+      else
+        llvm_unreachable("unexpected block declcontext");
 
       fields.push_back(createFieldType("this", type, 0, loc, AS_public,
                                        offsetInBits, tunit, tunit));