diff --git a/dev-blobserver b/dev-blobserver
index 2fc37ae6f..0b66c591d 100755
--- a/dev-blobserver
+++ b/dev-blobserver
@@ -15,7 +15,8 @@ GetOptions(
     "tls" => \$opt_tls,
     ) or usage();
 
-my $port = shift || "3179";
+my $port = shift;
+$port = "3179" unless defined($port);
 usage() unless $port =~ /^\d+$/;
 
 system("./build.pl", "server/go/camlistored") and die "Failed to build.\n";
@@ -38,6 +39,6 @@ $ENV{CAMLI_TLS_CRT_FILE} = $opt_tls ? "$Bin/config/dev-tls.crt" : "";
 $ENV{CAMLI_TLS_KEY_FILE} = $opt_tls ? "$Bin/config/dev-tls.key" : "";
 exec("$FindBin::Bin/server/go/camlistored/camlistored",
      "-configfile=$Bin/config/dev-blobserver-config.json",
-     "-listen=:$port",
+     "-listen=127.0.0.1:$port",
      @ARGV);
 
diff --git a/dev-server b/dev-server
index 3b005cdd0..505c65ce8 100755
--- a/dev-server
+++ b/dev-server
@@ -12,7 +12,8 @@ my $opt_wipe;
 GetOptions("wipe" => \$opt_wipe)
     or usage();
 
-my $port = shift || "3202";
+my $port = shift;
+$port = "3202" unless defined($port);
 usage() unless $port =~ /^\d+$/;
 
 system("./build.pl", "server/go/camlistored") and die "Failed to build camlistored";
@@ -51,5 +52,5 @@ $ENV{CAMLI_KEY_RING} = "$Bin/lib/go/camli/jsonsign/testdata/test-keyring.gpg";
 $ENV{CAMLI_SECRET_RING} = "$Bin/lib/go/camli/jsonsign/testdata/test-secring.gpg";
 exec("$FindBin::Bin/server/go/camlistored/camlistored",
      "-configfile=$Bin/config/dev-server-config.json",
-     "-listen=:$port",
+     "-listen=127.0.0.1:$port",
      @ARGV);
diff --git a/lib/go/camli/webserver/webserver.go b/lib/go/camli/webserver/webserver.go
index ffaae4141..a4c78b263 100644
--- a/lib/go/camli/webserver/webserver.go
+++ b/lib/go/camli/webserver/webserver.go
@@ -61,10 +61,13 @@ func (s *Server) BaseURL() string {
 	if s.enableTLS {
 		scheme = "https"
 	}
-	if strings.HasPrefix(*Listen, ":") {
-		return scheme + "://127.0.0.1" + *Listen
+	if s.listener != nil {
+		return scheme + "://" + s.listener.Addr().String()
 	}
-	return scheme + "://" + strings.Replace(*Listen, "0.0.0.0:", "127.0.0.1:", 1)
+	if strings.HasPrefix(*Listen, ":") {
+		return scheme + "://localhost" + *Listen
+	}
+	return scheme + "://" + strings.Replace(*Listen, "0.0.0.0:", "localhost:", 1)
 }
 
 // Register conditional handler-picker functions which get run before
@@ -94,8 +97,10 @@ func (s *Server) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 }
 
 func (s *Server) Serve() {
-	if os.Getenv("TESTING_PORT_WRITE_FD") == "" { // Don't make noise during unit tests
-		log.Printf("Starting to listen on %s\n", s.BaseURL())
+	doLog := os.Getenv("TESTING_PORT_WRITE_FD") == "" // Don't make noise during unit tests
+	base := s.BaseURL()
+	if doLog {
+		log.Printf("Starting to listen on %s\n", base)
 	}
 
 	var err os.Error
@@ -104,6 +109,10 @@ func (s *Server) Serve() {
 		log.Fatalf("Failed to listen on %s: %v", *Listen, err)
 	}
 
+	if doLog && strings.HasSuffix(base, ":0") {
+		log.Printf("Now listening on %s\n", s.BaseURL())
+	}
+
 	if s.enableTLS {
 		config := &tls.Config{
 			Rand:       rand.Reader,