diff --git a/operation.go b/operation.go
index 7b4e869..7255d14 100644
--- a/operation.go
+++ b/operation.go
@@ -19,12 +19,12 @@ func (e ErrInvalidOperator) Error() string {
 
 // operators holds custom operators
 var operators = make(map[string]OperatorFn)
-var operatorsWriteLock = &sync.Mutex{}
+var operatorsLock = &sync.RWMutex{}
 
 // AddOperator allows for custom operators to be used
 func AddOperator(key string, cb OperatorFn) {
-	operatorsWriteLock.Lock()
-	defer operatorsWriteLock.Unlock()
+	operatorsLock.Lock()
+	defer operatorsLock.Unlock()
 
 	operators[key] = func(values, data any) any {
 		return cb(parseValues(values, data), data)
@@ -32,7 +32,9 @@ func AddOperator(key string, cb OperatorFn) {
 }
 
 func operation(operator string, values, data any) any {
+	operatorsLock.RLock()
 	opFn, found := operators[operator]
+	operatorsLock.RUnlock()
 	if found {
 		return opFn(values, data)
 	}
@@ -43,8 +45,8 @@ func operation(operator string, values, data any) any {
 }
 
 func init() {
-	operatorsWriteLock.Lock()
-	defer operatorsWriteLock.Unlock()
+	operatorsLock.Lock()
+	defer operatorsLock.Unlock()
 
 	operators["and"] = _and
 	operators["or"] = _or
diff --git a/operation_test.go b/operation_test.go
new file mode 100644
index 0000000..ac1ad58
--- /dev/null
+++ b/operation_test.go
@@ -0,0 +1,75 @@
+package jsonlogic
+
+import (
+	"io"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// TestConcurrentApplyAndAddOperator validates that validating rules and adding operators concurrently
+// doesn't cause fatal errors or deadlocks.
+func TestConcurrentValidationAndAddOperator(t *testing.T) {
+	var wg sync.WaitGroup
+	numRoutines := 10
+	numIterations := 100
+
+	// Start multiple goroutines to validate rules concurrently
+	for i := 0; i < numRoutines; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for j := 0; j < numIterations; j++ {
+				rule := `{"==": [1, 1]}`
+				_ = IsValid(strings.NewReader(rule))
+			}
+		}()
+	}
+
+	// Start a goroutine to add a new operator concurrently
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for j := 0; j < numIterations; j++ {
+			AddOperator("test_op", func(values, data any) any {
+				return "test"
+			})
+		}
+	}()
+
+	wg.Wait()
+}
+
+// TestConcurrentApplyAndAddOperator validates that applying rules and adding operators concurrently
+// doesn't cause fatal errors or deadlocks.
+func TestConcurrentApplyAndAddOperator(t *testing.T) {
+	var wg sync.WaitGroup
+	numRoutines := 10
+	numIterations := 100
+
+	// Start multiple goroutines to apply rules concurrently
+	for i := 0; i < numRoutines; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for j := 0; j < numIterations; j++ {
+				rule := `{"==": [1, 1]}`
+				data := `{}`
+				_ = Apply(strings.NewReader(rule), strings.NewReader(data), io.Discard)
+			}
+		}()
+	}
+
+	// Start a goroutine to add a new operator concurrently
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for j := 0; j < numIterations; j++ {
+			AddOperator("test_op", func(values, data any) any {
+				return "test"
+			})
+		}
+	}()
+
+	wg.Wait()
+}
diff --git a/validator.go b/validator.go
index c0237ee..068edc2 100644
--- a/validator.go
+++ b/validator.go
@@ -64,7 +64,9 @@ func ValidateJsonLogic(rules any) bool {
 }
 
 func isOperator(op string) bool {
+	operatorsLock.RLock()
 	_, isOperator := operators[op]
+	operatorsLock.RUnlock()
 	return isOperator
 }