Index: lib/Analysis/ThreadSafetyCommon.cpp
===================================================================
--- lib/Analysis/ThreadSafetyCommon.cpp
+++ lib/Analysis/ThreadSafetyCommon.cpp
@@ -276,18 +276,31 @@
 
   // Function parameters require substitution and/or renaming.
   if (const auto *PV = dyn_cast_or_null<ParmVarDecl>(VD)) {
-    const auto *FD =
-        cast<FunctionDecl>(PV->getDeclContext())->getCanonicalDecl();
-    unsigned I = PV->getFunctionScopeIndex();
-
-    if (Ctx && Ctx->FunArgs && FD == Ctx->AttrDecl->getCanonicalDecl()) {
-      // Substitute call arguments for references to function parameters
-      assert(I < Ctx->NumArgs);
-      return translate(Ctx->FunArgs[I], Ctx->Prev);
+    if (isa<FunctionDecl>(PV->getDeclContext())) {
+      unsigned I = PV->getFunctionScopeIndex();
+      const auto *FD =
+          cast<FunctionDecl>(PV->getDeclContext())->getCanonicalDecl();
+      if (Ctx && Ctx->FunArgs && FD == Ctx->AttrDecl->getCanonicalDecl()) {
+        // Substitute call arguments for references to function parameters
+        assert(I < Ctx->NumArgs);
+        return translate(Ctx->FunArgs[I], Ctx->Prev);
+      }
+      // Map the param back to the param of the original function declaration
+      // for consistent comparisons.
+      VD = FD->getParamDecl(I);
+    } else {
+      unsigned I = PV->getFunctionScopeIndex();
+      const auto *FD =
+          cast<ObjCMethodDecl>(PV->getDeclContext())->getCanonicalDecl();
+      if (Ctx && Ctx->FunArgs && FD == Ctx->AttrDecl->getCanonicalDecl()) {
+        // Substitute call arguments for references to function parameters
+        assert(I < Ctx->NumArgs);
+        return translate(Ctx->FunArgs[I], Ctx->Prev);
+      }
+      // Map the param back to the param of the original function declaration
+      // for consistent comparisons.
+      VD = FD->getParamDecl(I);
     }
-    // Map the param back to the param of the original function declaration
-    // for consistent comparisons.
-    VD = FD->getParamDecl(I);
   }
 
   // For non-local variables, treat it as a reference to a named object.