diff --git a/slh-dsa/src/fors.rs b/slh-dsa/src/fors.rs
index 0a65eb6..3085c4d 100644
--- a/slh-dsa/src/fors.rs
+++ b/slh-dsa/src/fors.rs
@@ -486,7 +486,8 @@ mod tests {
 
         let idx_tree = rng.random_range(
             0..=(1u64
-                .wrapping_shl(Fors::H::U32 - Fors::HPrime::U32)
+                .checked_shl(Fors::H::U32 - Fors::HPrime::U32)
+                .unwrap_or(0)
                 .wrapping_sub(1)),
         );
         let idx_leaf = rng.random_range(0..(1 << (Fors::HPrime::USIZE)));
@@ -519,7 +520,8 @@ mod tests {
 
         let idx_tree = rng.random_range(
             0..=(1u64
-                .wrapping_shl(Fors::H::U32 - Fors::HPrime::U32)
+                .checked_shl(Fors::H::U32 - Fors::HPrime::U32)
+                .unwrap_or(0)
                 .wrapping_sub(1)),
         );
         let idx_leaf = rng.random_range(0..(1 << (Fors::HPrime::USIZE)));
diff --git a/slh-dsa/src/hypertree.rs b/slh-dsa/src/hypertree.rs
index 6e36cab..488f3cc 100644
--- a/slh-dsa/src/hypertree.rs
+++ b/slh-dsa/src/hypertree.rs
@@ -151,7 +151,8 @@ mod tests {
 
         let idx_tree = rng.random_range(
             0..=(1u64
-                .wrapping_shl(HTMode::H::U32 - HTMode::HPrime::U32)
+                .checked_shl(HTMode::H::U32 - HTMode::HPrime::U32)
+                .unwrap_or(0)
                 .wrapping_sub(1)),
         );
         let idx_leaf = rng.random_range(0..(1 << (HTMode::HPrime::USIZE)));
@@ -181,7 +182,8 @@ mod tests {
 
         let idx_tree = rng.random_range(
             0..=(1u64
-                .wrapping_shl(HTMode::H::U32 - HTMode::HPrime::U32)
+                .checked_shl(HTMode::H::U32 - HTMode::HPrime::U32)
+                .unwrap_or(0)
                 .wrapping_sub(1)),
         );
         let idx_leaf = rng.random_range(0..(1 << (HTMode::HPrime::USIZE)));