diff --git a/crates/core/src/token.rs b/crates/core/src/token.rs
index 1a13df9a3f..10fd8cab19 100644
--- a/crates/core/src/token.rs
+++ b/crates/core/src/token.rs
@@ -1015,15 +1015,6 @@ pub mod testing {
         }
     }
 
-    impl std::ops::Mul<Uint> for Amount {
-        type Output = Amount;
-
-        fn mul(mut self, rhs: Uint) -> Self::Output {
-            self.raw *= rhs;
-            self
-        }
-    }
-
     impl std::ops::Div<u64> for Amount {
         type Output = Self;
 
diff --git a/crates/core/src/uint.rs b/crates/core/src/uint.rs
index 68593e46f7..b22970d68c 100644
--- a/crates/core/src/uint.rs
+++ b/crates/core/src/uint.rs
@@ -511,7 +511,13 @@ impl FromStr for I256 {
 
     fn from_str(num: &str) -> Result<Self, Self::Err> {
         if let Some(("", neg_num)) = num.split_once('-') {
-            let uint = neg_num.parse::<Uint>()?.negate();
+            let (uint, overflow) = neg_num.parse::<Uint>()?.negate();
+            if overflow {
+                return Err(Box::new(std::io::Error::new(
+                    std::io::ErrorKind::InvalidData,
+                    "I256 overflow",
+                )));
+            }
             Ok(I256(uint))
         } else {
             let uint = num.parse::<Uint>()?;
@@ -522,8 +528,9 @@ impl FromStr for I256 {
 
 impl I256 {
     /// Compute the two's complement of a number.
-    pub fn negate(&self) -> Self {
-        Self(self.0.negate())
+    pub fn negate(&self) -> Option<Self> {
+        let (uint, overflow) = self.0.negate();
+        if overflow { None } else { Some(Self(uint)) }
     }
 
     /// Check if the amount is not negative (greater
@@ -1133,7 +1140,7 @@ mod test_uint {
 
     #[test]
     fn test_i256_str_roundtrip() {
-        let minus_one = I256::one().negate();
+        let minus_one = I256::one().negate().unwrap();
         let minus_one_str = minus_one.to_string();
         assert_eq!(minus_one_str, "-1");
 
diff --git a/crates/namada/src/ledger/protocol/mod.rs b/crates/namada/src/ledger/protocol/mod.rs
index 97ad0cc7e5..7a2d8fccb3 100644
--- a/crates/namada/src/ledger/protocol/mod.rs
+++ b/crates/namada/src/ledger/protocol/mod.rs
@@ -518,7 +518,7 @@ where
                     .map_err(|e| Error::FeeError(e.to_string()))?;
 
             let current_block_height =
-                state.in_mem().get_last_block_height() + 1;
+                state.in_mem().get_last_block_height().next_height();
 
             if let Some(post_bal) = balance.checked_sub(fees) {
                 token_transfer(
diff --git a/crates/sdk/src/masp.rs b/crates/sdk/src/masp.rs
index ccc220c85c..f7d3f19d24 100644
--- a/crates/sdk/src/masp.rs
+++ b/crates/sdk/src/masp.rs
@@ -51,7 +51,6 @@ use masp_proofs::prover::LocalTxProver;
 #[cfg(not(feature = "testing"))]
 use masp_proofs::sapling::SaplingVerificationContext;
 use namada_core::address::Address;
-use namada_core::arith::checked;
 use namada_core::collections::{HashMap, HashSet};
 use namada_core::dec::Dec;
 pub use namada_core::masp::{