diff --git a/include/SFML/System/String.hpp b/include/SFML/System/String.hpp
index d13341dde..de753f3ff 100644
--- a/include/SFML/System/String.hpp
+++ b/include/SFML/System/String.hpp
@@ -56,7 +56,7 @@ public:
     ////////////////////////////////////////////////////////////
     // NOLINTBEGIN(readability-identifier-naming)
     /// Represents an invalid position in the string
-    static constexpr std::size_t InvalidPos{std::basic_string<std::uint32_t>::npos};
+    static const std::size_t InvalidPos{std::basic_string<std::uint32_t>::npos};
     // NOLINTEND(readability-identifier-naming)
 
     ////////////////////////////////////////////////////////////
diff --git a/src/SFML/System/String.cpp b/src/SFML/System/String.cpp
index 0e44ebc65..64683b109 100644
--- a/src/SFML/System/String.cpp
+++ b/src/SFML/System/String.cpp
@@ -34,6 +34,10 @@
 
 namespace sf
 {
+////////////////////////////////////////////////////////////
+const std::size_t String::InvalidPos;
+
+
 ////////////////////////////////////////////////////////////
 String::String() = default;