1 files changed, 2 insertions, 0 deletions
diff --git a/cop.h b/cop.h
index d3f7194c2b..1ef5e0c492 100644
--- a/cop.h
+++ b/cop.h
@@ -357,6 +357,8 @@ typedef struct stackinfo PERL_SI;
 
 #define PUSHSTACK PUSHSTACKi(PERLSI_UNKNOWN)
 
+/* POPSTACK works with PL_stack_sp, so any local sp modifications may
+ * need to be flushed with a PUTBACK */
 #define POPSTACK \
     STMT_START {							\
 	djSP;								\