diff --git a/include/boost/charconv/detail/ryu/ryu_generic_128.hpp b/include/boost/charconv/detail/ryu/ryu_generic_128.hpp
index a677ec7..79008af 100644
--- a/include/boost/charconv/detail/ryu/ryu_generic_128.hpp
+++ b/include/boost/charconv/detail/ryu/ryu_generic_128.hpp
@@ -413,7 +413,7 @@ static inline int generic_to_chars(const struct floating_decimal_128 v, char* re
     return index;
 }
 
-static inline int generic_to_chars_fixed(const struct floating_decimal_128 v, char* result, const ptrdiff_t result_size, int) noexcept
+static inline int generic_to_chars_fixed(const struct floating_decimal_128 v, char* result, const ptrdiff_t result_size, int precision) noexcept
 {
     if (v.exponent == fd128_exceptional_exponent)
     {
@@ -469,6 +469,12 @@ static inline int generic_to_chars_fixed(const struct floating_decimal_128 v, ch
         current_len = -v.exponent + 2;
     }
 
+    if (current_len < precision)
+    {
+        memset(result + current_len, '0', precision - current_len);
+        current_len = precision;
+    }
+
     return current_len;
 }