diff --git a/flang/include/flang/Decimal/decimal.h b/flang/include/flang/Decimal/decimal.h
--- a/flang/include/flang/Decimal/decimal.h
+++ b/flang/include/flang/Decimal/decimal.h
@@ -105,17 +105,17 @@
     enum FortranRounding = RoundNearest, const char *end = nullptr);
 
 extern template ConversionToBinaryResult<8> ConvertToBinary<8>(
-    const char *&, enum FortranRounding, const char *end = nullptr);
+    const char *&, enum FortranRounding, const char *end);
 extern template ConversionToBinaryResult<11> ConvertToBinary<11>(
-    const char *&, enum FortranRounding, const char *end = nullptr);
+    const char *&, enum FortranRounding, const char *end);
 extern template ConversionToBinaryResult<24> ConvertToBinary<24>(
-    const char *&, enum FortranRounding, const char *end = nullptr);
+    const char *&, enum FortranRounding, const char *end);
 extern template ConversionToBinaryResult<53> ConvertToBinary<53>(
-    const char *&, enum FortranRounding, const char *end = nullptr);
+    const char *&, enum FortranRounding, const char *end);
 extern template ConversionToBinaryResult<64> ConvertToBinary<64>(
-    const char *&, enum FortranRounding, const char *end = nullptr);
+    const char *&, enum FortranRounding, const char *end);
 extern template ConversionToBinaryResult<113> ConvertToBinary<113>(
-    const char *&, enum FortranRounding, const char *end = nullptr);
+    const char *&, enum FortranRounding, const char *end);
 } // namespace Fortran::decimal
 extern "C" {
 #define NS(x) Fortran::decimal::x