diff --git a/lib/SIL/Utils/PrunedLiveness.cpp b/lib/SIL/Utils/PrunedLiveness.cpp
index 68b5bbe0953eb..6e55852ee6bdd 100644
--- a/lib/SIL/Utils/PrunedLiveness.cpp
+++ b/lib/SIL/Utils/PrunedLiveness.cpp
@@ -578,6 +578,11 @@ void MultiDefPrunedLiveness::findBoundariesInBlock(
         boundary.deadDefs.push_back(deadArg);
       }
     }
+    if (auto *predBB = block->getSinglePredecessorBlock()) {
+      if (getBlockLiveness(predBB) == PrunedLiveBlocks::LiveOut) {
+        boundary.boundaryEdges.push_back(block);
+      }
+    }
   }
   // All live-within blocks must contain a boundary.
   assert(isLiveOut
diff --git a/test/SILOptimizer/ossa_lifetime_analysis.sil b/test/SILOptimizer/ossa_lifetime_analysis.sil
index 1f90db7adb5ed..2271adbe2f53f 100644
--- a/test/SILOptimizer/ossa_lifetime_analysis.sil
+++ b/test/SILOptimizer/ossa_lifetime_analysis.sil
@@ -176,7 +176,9 @@ bb0(%0 : @guaranteed $D):
   return %99 : $()
 }
 
-// CHECK-LABEL: @testMultiDef
+// A LiveOut block with a non-SSA def, bb0, has no liveness boundary.
+//
+// CHECK-LABEL: @testMultiDefLiveOutNoBoundary
 // CHECK: MultiDef lifetime analysis:
 // CHECK:   def: [[CP0:%.*]] = copy_value %0 : $C
 // CHECK:   def: %{{.*}} = copy_value %0 : $C
@@ -187,12 +189,12 @@ bb0(%0 : @guaranteed $D):
 // CHECK: bb3: LiveWithin,
 // CHECK: bb4: LiveWithin,
 // CHECK: bb1: LiveWithin,
-// CHECK: lifetime-ending user:   %{{.*}} = move_value [[CP0]] : $C
-// CHECK: lifetime-ending user:   destroy_value [[CP0]] : $C
-// CHECK: lifetime-ending user:   br bb4(%5 : $C)
-// CHECK: lifetime-ending user:   br bb4(%7 : $C)
-// CHECK: lifetime-ending user:   destroy_value %9 : $C
-sil [ossa] @testMultiDef : $@convention(thin) (@guaranteed C) -> () {
+// CHECK: last user:   br bb4
+// CHECK-NEXT: last user:   br bb4
+// CHECK-NEXT: last user:   %{{.*}} = move_value [[CP0]] : $C
+// CHECK-NEXT: last user:   destroy_value %{{.*}} : $C
+// CHECK-NEXT: last user:   destroy_value [[CP0]] : $C
+sil [ossa] @testMultiDefLiveOutNoBoundary : $@convention(thin) (@guaranteed C) -> () {
 bb0(%0 : @guaranteed $C):
   %copy0 = copy_value %0 : $C
   debug_value [trace] %copy0 : $C
@@ -218,3 +220,33 @@ bb4(%phi : @owned $C):
   %99 = tuple()
   return %99 : $()
 }
+
+// A dead-end block with a def can still be a boundary edge. This can
+// only happen in OSSA with incomplete lifetimes.
+//
+// CHECK-LABEL: @testMultiDefDeadDefBoundaryEdge
+// CHECK: MultiDef lifetime analysis:
+// CHECK:   def: [[CP0:%.*]] = copy_value %0 : $C
+// CHECK:   def: [[CP3:%.*]] = copy_value %0 : $C
+// CHECK: bb0: LiveOut,
+// CHECK: bb1: LiveWithin,
+// CHECK: bb2: LiveWithin,
+// CHECK: last user:   destroy_value [[CP0]] : $C
+// CHECK-NEXT: boundary edge: bb1
+// CHECK-NEXT: dead def: [[CP3]] = copy_value %0 : $C
+sil [ossa] @testMultiDefDeadDefBoundaryEdge : $@convention(thin) (@guaranteed C) -> () {
+bb0(%0 : @guaranteed $C):
+  %copy0 = copy_value %0 : $C
+  debug_value [trace] %copy0 : $C
+  cond_br undef, bb1, bb3
+
+bb1:
+  %dead = copy_value %0 : $C
+  debug_value [trace] %dead : $C
+  unreachable
+
+bb3:
+  destroy_value %copy0 : $C
+  %99 = tuple()
+  return %99 : $()
+}