diff --git a/test/test_extractions.cpp b/test/test_extractions.cpp
index 8b2b64b..2ed550d 100644
--- a/test/test_extractions.cpp
+++ b/test/test_extractions.cpp
@@ -64,8 +64,8 @@ TEST_CASE("extract test functions for numbers with invalid inputs") {
     CHECK_INVALID_CONVERSION("xxx1", float);
 
     // number too big
-    CHECK_INVALID_CONVERSION((std::string{40, '1'} + "." +
-                              std::string{40, '2'}),
+    CHECK_INVALID_CONVERSION((std::string(40, '1') + "." +
+                              std::string(40, '2')),
                              double);
 
     // random input for int
diff --git a/test/test_extractions_without_fast_float.cpp b/test/test_extractions_without_fast_float.cpp
index 7e6660c..e3871a6 100644
--- a/test/test_extractions_without_fast_float.cpp
+++ b/test/test_extractions_without_fast_float.cpp
@@ -31,8 +31,8 @@ TEST_CASE("extract test functions for numbers with invalid inputs without fast "
     CHECK_INVALID_CONVERSION("xxx1", float);
 
     // number too big
-    CHECK_INVALID_CONVERSION((std::string{40, '1'} + "." +
-                              std::string{40, '2'}),
+    CHECK_INVALID_CONVERSION((std::string(40, '1') + "." +
+                              std::string(40, '2')),
                              double);
 }