diff --git a/Makefile b/Makefile
index 3163dad..6419212 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 .DEFAULT_GOAL := all
 
 .PHONY: all
-all: test lint
+all: test lint fuzz
 
 # the TEST_FLAGS env var can be set to eg run only specific tests
 .PHONY: test
@@ -12,6 +12,10 @@ test:
 bench:
 	go test -bench=.
 
+.PHONY: fuzz
+fuzz:
+	go test -fuzz=. -fuzztime=10s ./...
+
 .PHONY: lint
 lint:
 	golangci-lint run
diff --git a/json.go b/json.go
index f113e3f..b85c4a7 100644
--- a/json.go
+++ b/json.go
@@ -18,6 +18,10 @@ var (
 
 // MarshalJSON implements the json.Marshaler interface.
 func (om *OrderedMap[K, V]) MarshalJSON() ([]byte, error) { //nolint:funlen
+	if om == nil || om.list == nil {
+		return []byte("null"), nil
+	}
+
 	writer := jwriter.Writer{}
 	writer.RawByte('{')