diff --git a/argument.cpp b/argument.cpp
index c7d6043..2720da9 100644
--- a/argument.cpp
+++ b/argument.cpp
@@ -28,7 +28,6 @@
 
 const std::string ArgumentParser::true_string = "true";
 
-const char* ArgumentParser::optionstr = "p:?h";
 const option ArgumentParser::options[] = {
     {"path", required_argument, nullptr, 'p'},
     {"help", no_argument, nullptr, 'h'},
diff --git a/argument.hpp b/argument.hpp
index 040b022..c1a80d2 100644
--- a/argument.hpp
+++ b/argument.hpp
@@ -47,7 +47,7 @@
     static const option options[];
 
     /** @brief optstring as needed by getopt_long */
-    static const char* optionstr;
+    static inline const char* optionstr = "p:?h";
 };
 
 } // namespace led