diff --git a/build/build-clang/D116020.patch b/build/build-clang/D116020.patch
new file mode 100644
index 000000000000..648d5ef99c3a
--- /dev/null
+++ b/build/build-clang/D116020.patch
@@ -0,0 +1,39 @@
+Index: clang/lib/AST/Mangle.cpp
+===================================================================
+--- a/clang/lib/AST/Mangle.cpp
++++ b/clang/lib/AST/Mangle.cpp
+@@ -225,11 +225,17 @@
+   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
+     if (!MD->isStatic())
+       ++ArgWords;
+-  for (const auto &AT : Proto->param_types())
++  for (const auto &AT : Proto->param_types()) {
++    // If an argument type is incomplete there is no way to get its size to
++    // correctly encode into the mangling scheme.
++    // Follow GCCs behaviour by simply breaking out of the loop.
++    if (AT->isIncompleteType())
++      break;
+     // Size should be aligned to pointer size.
+     ArgWords +=
+         llvm::alignTo(ASTContext.getTypeSize(AT), TI.getPointerWidth(0)) /
+         TI.getPointerWidth(0);
++  }
+   Out << ((TI.getPointerWidth(0) / 8) * ArgWords);
+ }
+ 
+Index: clang/test/CodeGen/pr52782-stdcall-func-decl.cpp
+===================================================================
+--- /dev/null
++++ b/clang/test/CodeGen/pr52782-stdcall-func-decl.cpp
+@@ -0,0 +1,11 @@
++// RUN: %clang_cc1 -triple i686-w64-windows-gnu -o - -emit-llvm -debug-info-kind=constructor %s
++
++#define NS_IMETHOD_(type) type __stdcall
++
++enum nsresult {};
++
++class NotNull;
++
++class nsICanvasRenderingContextInternal {
++  NS_IMETHOD_(nsresult) InitializeWithDrawTarget(NotNull);
++} nsTBaseHashSet;
diff --git a/build/build-clang/clang-13.json b/build/build-clang/clang-13.json
index 0f1b41deeb9c..621e975ebb25 100644
--- a/build/build-clang/clang-13.json
+++ b/build/build-clang/clang-13.json
@@ -19,6 +19,7 @@
       "llvmorg-14-init-4465-g22ea0cea595e-v2.patch",
       "llvmorg-14-init-6706-g6404f4b5af39.patch",
       "llvmorg-14-init-9105-g3c47c5ca13b8.patch",
-      "llvmorg-14-init-11347-g93a20ecee4b6.patch"
+      "llvmorg-14-init-11347-g93a20ecee4b6.patch",
+      "D116020.patch"
     ]
 }