diff --git a/src/net/conf.go b/src/net/conf.go
index 01bb585..c92e579 100644
--- a/src/net/conf.go
+++ b/src/net/conf.go
@@ -19,7 +19,7 @@
 	// forceCgoLookupHost forces CGO to always be used, if available.
 	forceCgoLookupHost bool
 
-	netGo  bool // "netgo" build tag in use (or no cgo)
+	netGo  bool // go DNS resolution forced
 	netCgo bool // cgo DNS resolution forced
 
 	// machine has an /etc/mdns.allow file
@@ -112,6 +112,12 @@
 	}
 }
 
+// canUseCgo reports whether calling cgo functions is allowed
+// for non-hostname lookups.
+func (c *conf) canUseCgo() bool {
+	return c.hostLookupOrder("") == hostLookupCgo
+}
+
 // hostLookupOrder determines which strategy to use to resolve hostname.
 func (c *conf) hostLookupOrder(hostname string) (ret hostLookupOrder) {
 	if c.dnsDebugLevel > 1 {
diff --git a/src/net/lookup_unix.go b/src/net/lookup_unix.go
index 1c811d2..a64da8b 100644
--- a/src/net/lookup_unix.go
+++ b/src/net/lookup_unix.go
@@ -74,19 +74,21 @@
 }
 
 func lookupPort(network, service string) (int, error) {
-	port, err, ok := cgoLookupPort(network, service)
-	if !ok {
-		port, err = goLookupPort(network, service)
+	if systemConf().canUseCgo() {
+		if port, err, ok := cgoLookupPort(network, service); ok {
+			return port, err
+		}
 	}
-	return port, err
+	return goLookupPort(network, service)
 }
 
 func lookupCNAME(name string) (string, error) {
-	cname, err, ok := cgoLookupCNAME(name)
-	if !ok {
-		cname, err = goLookupCNAME(name)
+	if systemConf().canUseCgo() {
+		if cname, err, ok := cgoLookupCNAME(name); ok {
+			return cname, err
+		}
 	}
-	return cname, err
+	return goLookupCNAME(name)
 }
 
 func lookupSRV(service, proto, name string) (string, []*SRV, error) {
@@ -148,9 +150,10 @@
 }
 
 func lookupAddr(addr string) ([]string, error) {
-	ptrs, err, ok := cgoLookupPTR(addr)
-	if !ok {
-		ptrs, err = goLookupPTR(addr)
+	if systemConf().canUseCgo() {
+		if ptrs, err, ok := cgoLookupPTR(addr); ok {
+			return ptrs, err
+		}
 	}
-	return ptrs, err
+	return goLookupPTR(addr)
 }