diff --git a/src/heap.cc b/src/heap.cc
index b62c23d..d1cef1b 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -1,12 +1,8 @@
 #include "heap.h"
 
 // Records the given pointer and size in the current set of live ptrs,
-// associated with the current stack trace.
+// associated with the current stack trace. The GIL must be held.
 void HeapProfiler::RecordMalloc(void *ptr, size_t size) {
-  // The RAW allocator may be called without the GIL held.
-  // We may increase references to the filename fields in the
-  // code object when we save the trace, so we need to first ensure that
-  // the GIL is held.
   CallTrace trace;
   GetCurrentCallTrace(&trace, max_frames_);
   auto trace_handle = traces_.Intern(trace);
diff --git a/src/heap.h b/src/heap.h
index c2a9be2..fa1f358 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -81,6 +81,10 @@ inline void HeapProfiler::HandleMalloc(void *ptr, std::size_t size,
     return;
   }
 
+  // The RAW allocator may be called without the GIL held.
+  // We may increase references to the filename fields in the
+  // code object when we save the trace, so we need to first ensure that
+  // the GIL is held.
   PyGILState_STATE gil_state;
   if (is_raw) {
     gil_state = PyGILState_Ensure();