diff --git a/include/internal/catch_tostring.h b/include/internal/catch_tostring.h
index 02eb0d6f..6a20f9ef 100644
--- a/include/internal/catch_tostring.h
+++ b/include/internal/catch_tostring.h
@@ -180,7 +180,7 @@ namespace Catch {
     };
 
     template<>
-    struct StringMaker<nullptr_t> {
+    struct StringMaker<std::nullptr_t> {
         std::string operator()(std::nullptr_t);
     };
 
diff --git a/include/internal/catch_tostring.hpp b/include/internal/catch_tostring.hpp
index 8fc3c89e..06046095 100644
--- a/include/internal/catch_tostring.hpp
+++ b/include/internal/catch_tostring.hpp
@@ -197,7 +197,7 @@ std::string StringMaker<unsigned char>::operator()(unsigned char c) {
     return ::Catch::Detail::stringify(static_cast<char>(c));
 }
 
-std::string StringMaker<nullptr_t>::operator()(std::nullptr_t) {
+std::string StringMaker<std::nullptr_t>::operator()(std::nullptr_t) {
     return "nullptr";
 }