diff --git a/src/stores/mem.rs b/src/stores/mem.rs
index 0803757..95df8bd 100644
--- a/src/stores/mem.rs
+++ b/src/stores/mem.rs
@@ -9,7 +9,7 @@ impl MemActStore {
         MemActStore(HashMap::new())
     }
 
-    fn add_or_sub_balance(&mut self, client: &u16, amnt: usize, sub: bool) -> usize {
+    fn add_or_sub_balance(&mut self, client: &u16, amnt: isize, sub: bool) -> isize {
         let act = self
             .0
             .entry(*client)
@@ -24,15 +24,15 @@ impl MemActStore {
 }
 
 impl ActStore for MemActStore {
-    fn add_to_balance(&mut self, client: &u16, amnt: usize) -> usize {
+    fn add_to_balance(&mut self, client: &u16, amnt: isize) -> isize {
         self.add_or_sub_balance(client, amnt, false)
     }
 
-    fn sub_from_balance(&mut self, client: &u16, amnt: usize) -> usize {
+    fn sub_from_balance(&mut self, client: &u16, amnt: isize) -> isize {
         self.add_or_sub_balance(client, amnt, true)
     }
 
-    fn hold_amount(&mut self, client: u16, amnt: usize) {
+    fn hold_amount(&mut self, client: u16, amnt: isize) {
         todo!()
     }
 
diff --git a/src/stores/mod.rs b/src/stores/mod.rs
index bf7a316..2f92d15 100644
--- a/src/stores/mod.rs
+++ b/src/stores/mod.rs
@@ -6,9 +6,9 @@ use crate::types::Account;
 pub trait ActStore {
 
     fn get_account(&self, client: &u16) -> Option<&Account>;
-    fn add_to_balance(&mut self, client: &u16, amnt: usize) -> usize;
-    fn sub_from_balance(&mut self, client: &u16, amnt: usize) -> usize;
-    fn hold_amount(&mut self, client:u16, amnt: usize);
+    fn add_to_balance(&mut self, client: &u16, amnt: isize) -> isize;
+    fn sub_from_balance(&mut self, client: &u16, amnt: isize) -> isize;
+    fn hold_amount(&mut self, client:u16, amnt: isize);
     fn lock_account(&mut self, client: u16);
     fn unlock_account(&mut self, client: u16);