diff --git a/symbol/symbol.h b/symbol/symbol.h
index 173310fc83816bc1c919263942c8a4f7758f7bdb..d4529435e0332e0492f9c60fbe4e95b0b29f5921 100644
--- a/symbol/symbol.h
+++ b/symbol/symbol.h
@@ -35,6 +35,7 @@ struct Symbol {
 struct Stack {
     struct Symbol* symbol;  // symbol info for current stack
     struct Stack* next;     // points to next position in stack
+    struct Stack* prev;     // points to previous position in stack
     __u64 count;
 } __attribute__((aligned(64)));