diff --git a/fpga/include/villas/fpga/vlnv.hpp b/fpga/include/villas/fpga/vlnv.hpp
index ac865201d..0f6d1a752 100644
--- a/fpga/include/villas/fpga/vlnv.hpp
+++ b/fpga/include/villas/fpga/vlnv.hpp
@@ -41,7 +41,7 @@ public:
 	    version("")
 	{ }
 
-	Vlnv(std::string s)
+	Vlnv(const std::string &s)
 	{
 		parseFromString(s);
 	}