diff --git a/lldb/include/lldb/Core/ModuleList.h b/lldb/include/lldb/Core/ModuleList.h
--- a/lldb/include/lldb/Core/ModuleList.h
+++ b/lldb/include/lldb/Core/ModuleList.h
@@ -464,6 +464,12 @@
 
   static bool RemoveSharedModuleIfOrphaned(const Module *module_ptr);
 
+  /// Applies 'callback' to each module in this ModuleList.
+  /// If 'callback' returns false, iteration terminates.
+  /// The 'module_sp' passed to 'callback' is guaranteed to
+  /// be non-null.
+  ///
+  /// This function is thread-safe.
   void ForEach(std::function<bool(const lldb::ModuleSP &module_sp)> const
                    &callback) const;
 
diff --git a/lldb/source/Core/ModuleList.cpp b/lldb/source/Core/ModuleList.cpp
--- a/lldb/source/Core/ModuleList.cpp
+++ b/lldb/source/Core/ModuleList.cpp
@@ -1067,9 +1067,10 @@
 void ModuleList::ForEach(
     std::function<bool(const ModuleSP &module_sp)> const &callback) const {
   std::lock_guard<std::recursive_mutex> guard(m_modules_mutex);
-  for (const auto &module : m_modules) {
+  for (const auto &module_sp : m_modules) {
+    assert(module_sp != nullptr);
     // If the callback returns false, then stop iterating and break out
-    if (!callback(module))
+    if (!callback(module_sp))
       break;
   }
 }