diff --git a/src/base.rs b/src/base.rs
index 1147982..d84897d 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -621,9 +621,15 @@ impl IntermediateSymbolDecoder {
     }
 
     fn fma_rows(&mut self, i: usize, iprime: usize, beta: Octet) {
-        self.debug_symbol_mul_ops += 1;
-        let temp = self.D[self.d[i]].clone();
-        self.D[self.d[iprime]].fused_addassign_mul_scalar(&temp, &beta);
+        if beta == Octet::one() {
+            let temp = self.D[self.d[i]].clone();
+            self.D[self.d[iprime]] += &temp;
+        }
+        else {
+            self.debug_symbol_mul_ops += 1;
+            let temp = self.D[self.d[i]].clone();
+            self.D[self.d[iprime]].fused_addassign_mul_scalar(&temp, &beta);
+        }
         for j in 0..self.L {
             self.A[iprime][j] += &self.A[i][j] * β
         }
diff --git a/src/octet.rs b/src/octet.rs
index 361b31d..56f2fab 100644
--- a/src/octet.rs
+++ b/src/octet.rs
@@ -131,6 +131,12 @@ impl AddAssign for Octet {
     }
 }
 
+impl<'a> AddAssign<&'a Octet> for Octet {
+    fn add_assign(&mut self, other: &'a Octet) {
+        self.value ^= other.value;
+    }
+}
+
 impl Sub for Octet {
     type Output = Octet;
 
diff --git a/src/symbol.rs b/src/symbol.rs
index 75b704c..da72f03 100644
--- a/src/symbol.rs
+++ b/src/symbol.rs
@@ -64,10 +64,13 @@ impl Add for Symbol {
     }
 }
 
-impl AddAssign for Symbol {
-    fn add_assign(&mut self, other: Symbol) {
+impl<'a> AddAssign<&'a Symbol> for Symbol {
+    fn add_assign(&mut self, other: &'a Symbol) {
+        assert_eq!(self.value.len(), other.value.len());
         for i in 0..self.value.len() {
-            self.value[i] += other.value[i].clone();
+            unsafe {
+                *self.value.get_unchecked_mut(i) += other.value.get_unchecked(i);
+            }
         }
     }
 }