diff --git a/src/lib/netlist/nl_setup.cpp b/src/lib/netlist/nl_setup.cpp
index 1b0835d8cdc..adefdf96452 100644
--- a/src/lib/netlist/nl_setup.cpp
+++ b/src/lib/netlist/nl_setup.cpp
@@ -775,7 +775,7 @@ void setup_t::resolve_inputs()
 
 void setup_t::start_devices()
 {
-	pstring env = plib::util::environment("NL_LOGS");
+	pstring env = plib::util::environment("NL_LOGS", "");
 
 	if (env != "")
 	{
diff --git a/src/lib/netlist/plib/putil.h b/src/lib/netlist/plib/putil.h
index 9e79e958927..728a475dd28 100644
--- a/src/lib/netlist/plib/putil.h
+++ b/src/lib/netlist/plib/putil.h
@@ -18,7 +18,7 @@ namespace plib
 	namespace util
 	{
 		const pstring buildpath(std::initializer_list<pstring> list );
-		const pstring environment(const pstring &var, const pstring &default_val = "");
+		const pstring environment(const pstring &var, const pstring &default_val);
 	}
 
 	namespace container
diff --git a/src/lib/netlist/solver/nld_solver.cpp b/src/lib/netlist/solver/nld_solver.cpp
index d1f3bcc4eb8..12297dbd237 100644
--- a/src/lib/netlist/solver/nld_solver.cpp
+++ b/src/lib/netlist/solver/nld_solver.cpp
@@ -275,7 +275,7 @@ void NETLIB_NAME(solver)::post_start()
 	//m_params.m_max_timestep = std::max(m_params.m_max_timestep, m_params.m_max_timestep::)
 
 	// Override log statistics
-	pstring p = plib::util::environment("NL_STATS");
+	pstring p = plib::util::environment("NL_STATS", "");
 	if (p != "")
 		m_params.m_log_stats = p.as_long();
 	else