diff --git a/src/Val.cc b/src/Val.cc
index 62a40a6a50..ee706c0996 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -961,8 +961,7 @@ IPAddr SubNetVal::Mask() const
 
 bool SubNetVal::Contains(const IPAddr& addr) const
 	{
-	IPAddr a(addr);
-	return val.subnet_val->Contains(a);
+	return val.subnet_val->Contains(addr);
 	}
 
 Val* SubNetVal::DoClone(CloneState* state)
diff --git a/src/input/readers/config/Config.cc b/src/input/readers/config/Config.cc
index c215a44733..ab11f80487 100644
--- a/src/input/readers/config/Config.cc
+++ b/src/input/readers/config/Config.cc
@@ -176,7 +176,7 @@ bool Config::DoUpdate()
 	// keep a list of options to remove because they were no longer in the input file.
 	// Start out with all element and removes while going along
 	std::unordered_set<std::string> unseen_options;
-	for ( auto i : option_values )
+	for ( const auto& i : option_values )
 		{
 		unseen_options.insert(i.first);
 		}
@@ -282,7 +282,7 @@ bool Config::DoUpdate()
 		EndCurrentSend();
 
 	// clean up all options we did not see
-	for ( auto i : unseen_options )
+	for ( const auto& i : unseen_options )
 		option_values.erase(i);
 
 	return true;
diff --git a/src/probabilistic/CardinalityCounter.cc b/src/probabilistic/CardinalityCounter.cc
index 710bc86d21..a2d224a09e 100644
--- a/src/probabilistic/CardinalityCounter.cc
+++ b/src/probabilistic/CardinalityCounter.cc
@@ -173,7 +173,7 @@ bool CardinalityCounter::Merge(CardinalityCounter* c)
 	if ( m != c->GetM() )
 		return false;
 
-	const vector<uint8_t> temp = c->GetBuckets();
+	const vector<uint8_t>& temp = c->GetBuckets();
 
 	V = 0;
 
diff --git a/src/zeekygen/Target.cc b/src/zeekygen/Target.cc
index 85071b31e7..34c3df6c9f 100644
--- a/src/zeekygen/Target.cc
+++ b/src/zeekygen/Target.cc
@@ -23,7 +23,7 @@ using namespace zeekygen;
 
 static void write_plugin_section_heading(FILE* f, const plugin::Plugin* p)
 	{
-	string name = p->Name();
+	const string& name = p->Name();
 
 	fprintf(f, "%s\n", name.c_str());
 	for ( size_t i = 0; i < name.size(); ++i )