diff --git a/api/main_test.go b/api/main_test.go
index b395be0..9e08553 100644
--- a/api/main_test.go
+++ b/api/main_test.go
@@ -7,7 +7,7 @@ import (
 func TestInvalidIP(t *testing.T) {
 	_, err := generateJSON("foo")
 	errwant := "invalid IP"
-	if err.Error() != errwant {
+	if err == nil || err.Error() != errwant {
 		t.Fatalf(`generateJSON("foo") == "%v", wants "%s"`, err, errwant)
 	}
 }
@@ -15,7 +15,7 @@ func TestInvalidIP(t *testing.T) {
 func TestInaccessibleIP(t *testing.T) {
 	_, err := generateJSON("0.0.0.0")
 	errwant := "unspecified IP"
-	if err.Error() != errwant {
+	if err == nil || err.Error() != errwant {
 		t.Fatalf(`generateJSON("0.0.0.0") == "%v", wants "%s"`, err, errwant)
 	}
 }