diff --git a/fuzzers/FRET/src/systemstate/stg.rs b/fuzzers/FRET/src/systemstate/stg.rs
index 74429db714..56a35704f2 100644
--- a/fuzzers/FRET/src/systemstate/stg.rs
+++ b/fuzzers/FRET/src/systemstate/stg.rs
@@ -361,7 +361,7 @@ where
 
 //============================= Graph Feedback
 
-pub const STG_MAP_SIZE: usize = 1<<20;
+pub const STG_MAP_SIZE: usize = 1<<28; // 512MB
 pub static mut STG_MAP: [u16; STG_MAP_SIZE] = [0; STG_MAP_SIZE];
 pub static mut MAX_STG_NUM: usize = 0;
 pub unsafe fn stg_map_mut_slice<'a>() -> OwnedMutSlice<'a, u16> {
@@ -433,7 +433,11 @@ fn set_observer_map(trace : &Vec<EdgeIndex>) {
             if MAX_STG_NUM < i.index() {
                 MAX_STG_NUM = i.index();
             }
-            STG_MAP[i.index()] = STG_MAP[i.index()].saturating_add(1);
+            if i.index() < STG_MAP.len() {
+                STG_MAP[i.index()] = STG_MAP[i.index()].saturating_add(1);
+            } else {
+                eprintln!("STG Map index out of bounds: {}", i.index());
+            }
         }
     }
 }