diff --git a/Jenkinsfile b/Jenkinsfile
index abb132b..be4726b 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -47,8 +47,12 @@ pipeline {
                         env.GIT_PATH = env.GIT_PATH.substring(1)
                     }
                     if(env.GIT_PATH.startsWith("~/")) {
-                        env.GIT_PATH = env.GIT_PATH.substring(2, (env.GIT_PATH.length() - 1))
+                        env.GIT_PATH = env.GIT_PATH.substring(2)
                     }
+                    if(env.GIT_PATH.contains("../")) {
+                        error("GIT_PATH must not contain '../'")
+                    ]
+                    
                     // be sure branch is set
                     env.GIT_BRANCH = params.GIT_BRANCH ?: '*/master'
                 }