diff --git a/include/fast_float/bigint.h b/include/fast_float/bigint.h
index 45e7299..3040c50 100644
--- a/include/fast_float/bigint.h
+++ b/include/fast_float/bigint.h
@@ -535,19 +535,17 @@ struct bigint : pow5_tables<> {
       // we can't shift more than the capacity of the vector.
       return false;
     }
-    if (vec.is_empty()) {
-      // nothing to do
-      return true;
+    if (!vec.is_empty()) {
+      // move limbs
+      limb *dst = vec.data + n;
+      limb const *src = vec.data;
+      std::copy_backward(src, src + vec.len(), dst + vec.len());
+      // fill in empty limbs
+      limb *first = vec.data;
+      limb *last = first + n;
+      ::std::fill(first, last, 0);
+      vec.set_len(limb_t(n + vec.len()));
     }
-    // move limbs
-    limb *dst = vec.data + n;
-    limb const *src = vec.data;
-    std::copy_backward(src, src + vec.len(), dst + vec.len());
-    // fill in empty limbs
-    limb *first = vec.data;
-    limb *last = first + n;
-    ::std::fill(first, last, 0);
-    vec.set_len(limb_t(n + vec.len()));
     return true;
   }
 
@@ -590,12 +588,14 @@ struct bigint : pow5_tables<> {
   FASTFLOAT_CONSTEXPR20 bool add(limb y) noexcept { return small_add(vec, y); }
 
   // multiply as if by 2 raised to a power.
-  FASTFLOAT_CONSTEXPR20 bool pow2(am_pow_t exp) noexcept {
+  FASTFLOAT_CONSTEXPR20 bool pow2(am_pow_t const exp) noexcept {
+    FASTFLOAT_ASSERT(exp >= 0);
     return shl(static_cast<fast_float::bigint_bits_t>(exp));
   }
 
   // multiply as if by 5 raised to a power.
   FASTFLOAT_CONSTEXPR20 bool pow5(am_pow_t exp) noexcept {
+    FASTFLOAT_ASSERT(exp >= 0);
     // multiply by a power of 5
     limb_t const large_length = sizeof(large_power_of_5) / sizeof(limb);
     limb_span const large = limb_span(large_power_of_5, large_length);
@@ -627,6 +627,7 @@ struct bigint : pow5_tables<> {
 
   // multiply as if by 10 raised to a power.
   FASTFLOAT_CONSTEXPR20 bool pow10(am_pow_t exp) noexcept {
+    FASTFLOAT_ASSERT(exp >= 0);
     FASTFLOAT_TRY(pow5(exp));
     return pow2(exp);
   }
diff --git a/include/fast_float/digit_comparison.h b/include/fast_float/digit_comparison.h
index 2ccda2a..fa39efd 100644
--- a/include/fast_float/digit_comparison.h
+++ b/include/fast_float/digit_comparison.h
@@ -373,11 +373,9 @@ inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa positive_digit_comp(
 // we then need to scale by `2^(f- e)`, and then the two significant digits
 // are of the same magnitude.
 template <typename T>
-inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa negative_digit_comp(
-    bigint &bigmant, adjusted_mantissa am, am_pow_t const exponent) noexcept {
-  bigint &real_digits = bigmant;
-  am_pow_t const &real_exp = exponent;
-
+inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa
+negative_digit_comp(bigint &real_digits, adjusted_mantissa am,
+                    am_pow_t const real_exp) noexcept {
   // get the value of `b`, rounded down, and get a bigint representation of
   // b+h
   adjusted_mantissa am_b = am;
@@ -391,12 +389,12 @@ inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa negative_digit_comp(
       false,
 #endif
       am_b, b);
-  adjusted_mantissa theor = to_extended_halfway(b);
+  adjusted_mantissa const theor = to_extended_halfway(b);
   bigint theor_digits(theor.mantissa);
-  am_pow_t theor_exp = theor.power2;
+  am_pow_t const theor_exp = theor.power2;
 
   // scale real digits and theor digits to be same power.
-  am_pow_t pow2_exp = theor_exp - real_exp;
+  am_pow_t const pow2_exp = theor_exp - real_exp;
   am_pow_t pow5_exp = -real_exp;
   if (pow5_exp != 0) {
     FASTFLOAT_ASSERT(theor_digits.pow5(pow5_exp));
@@ -408,7 +406,7 @@ inline FASTFLOAT_CONSTEXPR20 adjusted_mantissa negative_digit_comp(
   }
 
   // compare digits, and use it to direct rounding
-  int ord = real_digits.compare(theor_digits);
+  int const ord = real_digits.compare(theor_digits);
   round<T>(am, [ord](adjusted_mantissa &a, am_pow_t shift) {
     round_nearest_tie_even(
         a, shift, [ord](bool is_odd, bool _, bool __) -> bool {