diff --git a/lldb/source/Target/ThreadPlanStack.cpp b/lldb/source/Target/ThreadPlanStack.cpp
--- a/lldb/source/Target/ThreadPlanStack.cpp
+++ b/lldb/source/Target/ThreadPlanStack.cpp
@@ -142,7 +142,10 @@
 lldb::ThreadPlanSP ThreadPlanStack::PopPlan() {
   assert(m_plans.size() > 1 && "Can't pop the base thread plan");
 
-  lldb::ThreadPlanSP plan_sp = std::move(m_plans.back());
+  // Note that `std::move` on `m_plans` elements can break its non-null
+  // invariant - if also calling functions (such as `WillPop`) that can't
+  // guarantee `m_plans` is not accessed in its inconsistent state.
+  lldb::ThreadPlanSP plan_sp = m_plans.back();
   m_completed_plans.push_back(plan_sp);
   plan_sp->WillPop();
   m_plans.pop_back();
@@ -152,7 +155,10 @@
 lldb::ThreadPlanSP ThreadPlanStack::DiscardPlan() {
   assert(m_plans.size() > 1 && "Can't discard the base thread plan");
 
-  lldb::ThreadPlanSP plan_sp = std::move(m_plans.back());
+  // Note that `std::move` on `m_plans` elements can break its non-null
+  // invariant - if also calling functions (such as `WillPop`) that can't
+  // guarantee `m_plans` is not accessed in its inconsistent state.
+  lldb::ThreadPlanSP plan_sp = m_plans.back();
   m_discarded_plans.push_back(plan_sp);
   plan_sp->WillPop();
   m_plans.pop_back();