diff --git a/common/shell-local/config.go b/common/shell-local/config.go
index b4fae91a4..410f6bb43 100644
--- a/common/shell-local/config.go
+++ b/common/shell-local/config.go
@@ -176,7 +176,7 @@ func Validate(config *Config) error {
 			}
 			if supported_os != true {
 				return fmt.Errorf("Invalid OS specified in only_on: '%s'\n"+
-					"Supported OS names: %v", provided_os, supported_syslist)
+					"Supported OS names: %s", provided_os, strings.Join(supported_syslist, ", "))
 			}
 		}
 	}