diff --git a/include/fast_float/ascii_number.h b/include/fast_float/ascii_number.h
index 689c908..bd072c6 100644
--- a/include/fast_float/ascii_number.h
+++ b/include/fast_float/ascii_number.h
@@ -241,6 +241,10 @@ fastfloat_really_inline decimal parse_decimal(const char *p, const char *pend) n
     answer.truncated = true;
     answer.num_digits = max_digits;
   }
+  // In very rare cases, we may have fewer than 19 digits, we want to be able to reliably
+  // assume that all digits up to max_digit_without_overflow have been initialized.
+  for(uint32_t i = answer.num_digits; i < max_digit_without_overflow; i++) { answer.digits[i] = 0; }
+
   return answer;
 }
 } // namespace fast_float
diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h
index 09917ad..d44b06d 100644
--- a/include/fast_float/float_common.h
+++ b/include/fast_float/float_common.h
@@ -149,9 +149,10 @@ struct decimal {
   // Moves are allowed:
   decimal(decimal &&) = default;
   decimal &operator=(decimal &&other) = default;
-  // Generates a mantissa by truncating to 19 digits; this function assumes
-  // that num_digits >= 19 (the caller is responsible for the check).
+  // Generates a mantissa by truncating to 19 digits.
   // This function should be reasonably fast.
+  // Note that the user is responsible to ensure that digits are
+  // initialized to zero when there are fewer than 19.
   inline uint64_t to_truncated_mantissa() {
     uint64_t val;
     // 8 first digits