diff --git a/rpc/server.go b/rpc/server.go
index 432a7b65..acb2095b 100644
--- a/rpc/server.go
+++ b/rpc/server.go
@@ -3,7 +3,9 @@ package rpc
 import (
 	"context"
 	"crypto/tls"
+	"errors"
 	"fmt"
+	"math"
 	"net"
 	"runtime/debug"
 	"strings"
@@ -116,12 +118,25 @@ func (s *Server) Send(ctx context.Context, in *proto.NotificationRequest) (*prot
 		}
 	}()
 
+	counts, err := safeIntToInt32(len(notification.Tokens))
+	if err != nil {
+		return nil, status.Error(codes.InvalidArgument, err.Error())
+	}
+
 	return &proto.NotificationReply{
 		Success: true,
-		Counts:  int32(len(notification.Tokens)),
+		Counts:  counts,
 	}, nil
 }
 
+// safeIntToInt32 converts an int to an int32, returning an error if the int is out of range.
+func safeIntToInt32(n int) (int32, error) {
+	if n < math.MinInt32 || n > math.MaxInt32 {
+		return 0, errors.New("integer overflow: value out of int32 range")
+	}
+	return int32(n), nil
+}
+
 // RunGRPCServer run gorush grpc server
 func RunGRPCServer(ctx context.Context, cfg *config.ConfYaml) error {
 	if !cfg.GRPC.Enabled {
diff --git a/rpc/server_test.go b/rpc/server_test.go
index 56d6f512..5cf878d2 100644
--- a/rpc/server_test.go
+++ b/rpc/server_test.go
@@ -1,5 +1,38 @@
 package rpc
 
+import (
+	"math"
+	"testing"
+)
+
+func TestSafeIntToInt32(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   int
+		want    int32
+		wantErr bool
+	}{
+		{"Valid int32", 123, 123, false},
+		{"Max int32", math.MaxInt32, math.MaxInt32, false},
+		{"Min int32", math.MinInt32, math.MinInt32, false},
+		{"Overflow int32", math.MaxInt32 + 1, 0, true},
+		{"Underflow int32", math.MinInt32 - 1, 0, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := safeIntToInt32(tt.input)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("safeIntToInt32() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("safeIntToInt32() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
 // const gRPCAddr = "localhost:9000"
 
 // func initTest() *config.ConfYaml {