Index: clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.h
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.h
+++ clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.h
@@ -263,7 +263,8 @@
 
   mutable std::unique_ptr<RetainSummaryManager> Summaries;
 public:
-  static constexpr const char *DeallocTagDescription = "DeallocSent";
+  static constexpr const char *DeallocTagDescription = "DeallocSentRCC";
+  static constexpr const char *DynamicCastFailTagDescription = "CastFailRCC";
 
   /// Track Objective-C and CoreFoundation objects.
   bool TrackObjCAndCFObjects = false;
Index: clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp
@@ -905,7 +905,9 @@
       NullOutputState = NullOutputState->BindExpr(
           CE, LCtx, C.getSValBuilder().makeNull(), /*Invalidate=*/false);
 
-      C.addTransition(NullOutputState);
+      static CheckerProgramPointTag CastFailTag(this,
+                                                DynamicCastFailTagDescription);
+      C.addTransition(NullOutputState, &CastFailTag);
 
       // And on the original branch assume that both input and
       // output are non-zero.
Index: clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountDiagnostics.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountDiagnostics.cpp
+++ clang/lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountDiagnostics.cpp
@@ -508,6 +508,12 @@
   bool DeallocSent = false;
 
   const ProgramPointTag *Tag = N->getLocation().getTag();
+
+  if (Tag && Tag->getTagDescription().contains(
+                 RetainCountChecker::DynamicCastFailTagDescription)) {
+    os << "Assuming dynamic cast returns null due to type mismatch";
+  }
+
   if (Tag && Tag->getTagDescription().contains(
                  RetainCountChecker::DeallocTagDescription)) {
     // We only have summaries attached to nodes after evaluating CallExpr and
Index: clang/test/Analysis/osobject-retain-release.cpp
===================================================================
--- clang/test/Analysis/osobject-retain-release.cpp
+++ clang/test/Analysis/osobject-retain-release.cpp
@@ -488,7 +488,7 @@
 
 void check_dynamic_cast_null_branch(OSObject *obj) {
   OSArray *arr1 = OSArray::withCapacity(10); // expected-note{{Call to method 'OSArray::withCapacity' returns an OSObject}}
-  OSArray *arr = OSDynamicCast(OSArray, obj);
+  OSArray *arr = OSDynamicCast(OSArray, obj); // expected-note{{Assuming dynamic cast returns null due to type mismatch}}
   if (!arr) // expected-note{{Taking true branch}}
     return; // expected-warning{{Potential leak of an object stored into 'arr1'}}
             // expected-note@-1{{Object leaked}}
@@ -499,6 +499,7 @@
   OSArray *arr = OSDynamicCast(OSArray, OSObject::generateObject(1)); // expected-note{{Call to method 'OSObject::generateObject' returns an OSObject}}
     // expected-warning@-1{{Potential leak of an object}}
     // expected-note@-2{{Object leaked}}
+    // expected-note@-3{{Assuming dynamic cast returns null due to type mismatch}}
   if (!arr)
     return;
   arr->release();