diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 59a65c13..9b739635 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -539,7 +539,7 @@ FMT_FUNC bool grisu2_gen_digits(
 #endif
 
 struct gen_digits_params {
-  unsigned num_digits;
+  int num_digits;
   bool fixed;
   bool upper;
   bool trailing_zeros;
@@ -617,11 +617,11 @@ struct fill {
 // The number is given as v = f * pow(10, exp), where f has size digits.
 template <typename Handler>
 FMT_FUNC void grisu2_prettify(const gen_digits_params &params,
-                              ptrdiff_t size, int exp, Handler &&handler) {
+                              int size, int exp, Handler &&handler) {
   if (!params.fixed) {
     // Insert a decimal point after the first digit and add an exponent.
     handler.insert(1, '.');
-    exp += static_cast<int>(size) - 1;
+    exp += size - 1;
     if (size < params.num_digits)
       handler.append(params.num_digits - size, '0');
     handler.append(params.upper ? 'E' : 'e');
@@ -629,13 +629,12 @@ FMT_FUNC void grisu2_prettify(const gen_digits_params &params,
     return;
   }
   // pow(10, full_exp - 1) <= v <= pow(10, full_exp).
-  int int_size = static_cast<int>(size);
-  int full_exp = int_size + exp;
+  int full_exp = size + exp;
   const int exp_threshold = 21;
-  if (int_size <= full_exp && full_exp <= exp_threshold) {
+  if (size <= full_exp && full_exp <= exp_threshold) {
     // 1234e7 -> 12340000000[.0+]
-    handler.append(full_exp - int_size, '0');
-    int num_zeros = static_cast<int>(params.num_digits) - full_exp;
+    handler.append(full_exp - size, '0');
+    int num_zeros = params.num_digits - full_exp;
     if (num_zeros > 0 && params.trailing_zeros) {
       handler.append('.');
       handler.append(num_zeros, '0');