diff --git a/double-conversion/strtod.cc b/double-conversion/strtod.cc
--- a/double-conversion/strtod.cc
+++ b/double-conversion/strtod.cc
@@ -436,16 +436,17 @@ static bool ComputeGuess(Vector<const ch
     return true;
   }
   if (*guess == Double::Infinity()) {
     return true;
   }
   return false;
 }
 
+#ifdef DEBUG
 static bool IsDigit(const char d) {
   return ('0' <= d) && (d <= '9');
 }
 
 static bool IsNonZeroDigit(const char d) {
   return ('1' <= d) && (d <= '9');
 }
 
@@ -457,16 +458,17 @@ static bool IsNonZeroDigit(const char d)
 static bool AssertTrimmedDigits(const Vector<const char>& buffer) {
   for(int i = 0; i < buffer.length(); ++i) {
     if(!IsDigit(buffer[i])) {
       return false;
     }
   }
   return (buffer.length() == 0) || (IsNonZeroDigit(buffer[0]) && IsNonZeroDigit(buffer[buffer.length()-1]));
 }
+#endif
 
 double StrtodTrimmed(Vector<const char> trimmed, int exponent) {
   DOUBLE_CONVERSION_ASSERT(trimmed.length() <= kMaxSignificantDecimalDigits);
   DOUBLE_CONVERSION_ASSERT(AssertTrimmedDigits(trimmed));
   double guess;
   const bool is_correct = ComputeGuess(trimmed, exponent, &guess);
   if (is_correct) {
     return guess;