diff --git a/include/CLI/TypeTools.hpp b/include/CLI/TypeTools.hpp
index fecdbafd..80d72622 100644
--- a/include/CLI/TypeTools.hpp
+++ b/include/CLI/TypeTools.hpp
@@ -140,11 +140,12 @@ template <typename T,
 bool lexical_cast(std::string input, T &output) {
 
 // On GCC 4.7, thread_local is not available, so this optimization
-// is turned off (avoiding multiple initialisations on multiple usages
+// is turned off (avoiding multiple initialisations on multiple usages)
 #if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER) && __GNUC__ == 4 && (__GNUC_MINOR__ < 8)
     std::istringstream is;
 #else
     static thread_local std::istringstream is;
+    is.clear();
 #endif
 
     is.str(input);