diff --git a/src/cryptoki.hxx b/src/cryptoki.hxx
index c9eaa45..7aed7a0 100644
--- a/src/cryptoki.hxx
+++ b/src/cryptoki.hxx
@@ -587,7 +587,7 @@ namespace cryptoki {
   };
 
   struct TokenInfo; // forward declaration
-  std::ostream& operator<<(std::ostream& out, const TokenInfo& ti);
+  inline std::ostream& operator<<(std::ostream& out, const TokenInfo& ti);
 
   struct TokenInfo {
       FixString<32> label;
@@ -638,7 +638,7 @@ namespace cryptoki {
 
   };
 
-  std::ostream& operator<<(std::ostream& out, const TokenInfo& ti) {
+  inline std::ostream& operator<<(std::ostream& out, const TokenInfo& ti) {
     return out
       <<"label="<<ti.label<<std::endl
       <<"manufacturerID="<<ti.manufacturerID<<std::endl