diff --git a/cmd/main.go b/cmd/main.go
index d8e5f7bc..54d11d88 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -137,7 +137,9 @@ func loadConfig(configFile, adapterName string) ([]byte, error) {
 	// as a special case, if a config file called "Caddyfile" was
 	// specified, and no adapter is specified, assume caddyfile adapter
 	// for convenience
-	if filepath.Base(configFile) == "Caddyfile" && adapterName == "" {
+	if strings.HasPrefix(filepath.Base(configFile), "Caddyfile") &&
+		filepath.Ext(configFile) != ".json" &&
+		adapterName == "" {
 		adapterName = "caddyfile"
 	}