diff --git a/fuzzers/wcet_qemu_sys/src/worst.rs b/fuzzers/wcet_qemu_sys/src/worst.rs
index 8d9eb3024f..1d1d0d73f5 100644
--- a/fuzzers/wcet_qemu_sys/src/worst.rs
+++ b/fuzzers/wcet_qemu_sys/src/worst.rs
@@ -212,7 +212,7 @@ where
 {
     /// Creates a new [`HitFeedback`]
     #[must_use]
-    pub fn new(target_map: HashMap<(u64,u64),T>, target_msd: f64, _map_observer: &O) -> Self {
+    pub fn new(target_map: HashMap<(u64,u64),T>, target_msd: f64, _map_observer: &QemuHashMapObserver<O, T>) -> Self {
         Self {target_map: target_map, target_msd: target_msd, phantom: PhantomData}
     }
 }
@@ -355,7 +355,7 @@ where
 {
     /// Creates a new [`HitImprovingFeedback`]
     #[must_use]
-    pub fn new(target_map: HashMap<(u64,u64),T>, _map_observer: &O) -> Self {
+    pub fn new(target_map: HashMap<(u64,u64),T>, _map_observer: &QemuHashMapObserver<O, T>) -> Self {
         Self {target_map: target_map, best_msd: f64::MAX, phantom: PhantomData}
     }
 }
@@ -422,10 +422,10 @@ where
 {
     /// Creates a new [`HitFeedback`]
     #[must_use]
-    pub fn new(_map_observer: &O) -> Self {
+    pub fn new(_map_observer: &QemuHashMapObserver<O, T>) -> Self {
         Self {dumpfile: None, phantom: PhantomData}
     }
-    pub fn with_dump(dumpfile: Option<PathBuf>,_map_observer: &O) -> Self {
+    pub fn with_dump(dumpfile: Option<PathBuf>,_map_observer: &QemuHashMapObserver<O, T>) -> Self {
         Self {dumpfile: dumpfile, phantom: PhantomData}
     }
 }