Problem when terraform init

When I execute `terraform init` I get : 
```
Initializing modules...
- module.security_group
Error downloading modules: Error loading modules: module security_group: Error parsing .terraform/modules/5495c1a2995d7628676059492e714f1a/terraform-aws-security-group-3.4.0/main.tf: At 5:16: Unknown token: 5:16 IDENT concat
```