diff --git a/clang/lib/Analysis/LifetimeSafety/Dataflow.h b/clang/lib/Analysis/LifetimeSafety/Dataflow.h
index fc3049c8bec84..aaa2c32c400c3 100644
--- a/clang/lib/Analysis/LifetimeSafety/Dataflow.h
+++ b/clang/lib/Analysis/LifetimeSafety/Dataflow.h
@@ -47,6 +47,9 @@ using ProgramPoint = const Fact *;
 ///   lifetime-relevant `Fact` transforms the lattice state. Only overloads
 ///   for facts relevant to the analysis need to be implemented.
 ///
+/// It may additionally override `Lattice exitBlock(Lattice);` to drop state
+/// that is not visible outside the block it was computed in.
+///
 /// \tparam Derived The CRTP derived class that implements the specific
 /// analysis.
 /// \tparam LatticeType The dataflow lattice used by the analysis.
@@ -157,7 +160,7 @@ class DataflowAnalysis {
         State = transferFact(State, F);
       }
     }
-    return State;
+    return static_cast<Derived *>(this)->exitBlock(State);
   }
 
   Lattice transferFact(Lattice In, const Fact *F) {
@@ -187,6 +190,8 @@ class DataflowAnalysis {
   }
 
 public:
+  Lattice exitBlock(Lattice In) { return In; }
+
   Lattice transfer(Lattice In, const IssueFact &) { return In; }
   Lattice transfer(Lattice In, const ExpireFact &) { return In; }
   Lattice transfer(Lattice In, const OriginFlowFact &) { return In; }
diff --git a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
index 078892bd48c10..f028e0f06ae29 100644
--- a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
@@ -148,8 +148,9 @@ class AnalysisImpl
   Lattice getInitialState() { return Lattice{}; }
 
   /// Merges two lattices by taking the union of loans for each origin.
-  /// Only persistent origins are joined; block-local origins are discarded.
   Lattice join(Lattice A, Lattice B) {
+    assert(A.BlockLocalOrigins.isEmpty() && B.BlockLocalOrigins.isEmpty() &&
+           "block-local origins must not reach a block boundary");
     OriginLoanMap JoinedOrigins = utils::join(
         A.PersistentOrigins, B.PersistentOrigins, OriginLoanMapFactory,
         [&](const LoanSet *S1, const LoanSet *S2) {
@@ -166,6 +167,14 @@ class AnalysisImpl
     return Lattice(JoinedOrigins, OriginLoanMapFactory.getEmptyMap());
   }
 
+  /// Block-local origins are not referenced outside the block that computed
+  /// them, so they are dropped here rather than propagated to adjacent blocks.
+  /// Dropping them at the boundary (instead of in `join`) also covers edges
+  /// where `join` is never called, such as blocks with a single predecessor.
+  Lattice exitBlock(Lattice L) {
+    return Lattice(L.PersistentOrigins, OriginLoanMapFactory.getEmptyMap());
+  }
+
   /// A new loan is issued to the origin. Old loans are erased.
   Lattice transfer(Lattice In, const IssueFact &F) {
     OriginID OID = F.getOriginID();