diff --git a/SwiftShell/File.swift b/SwiftShell/File.swift
index 1cc51f0..2df5d96 100644
--- a/SwiftShell/File.swift
+++ b/SwiftShell/File.swift
@@ -64,8 +64,12 @@ public func open(path: String, mode: FileMode = .Read) -> File {
 	}
 
 	// file may be nil if for instance path is invalid
-	// TODO: it physically pains me to write the next line. Proper error handling is forthcoming.
-	assert( file != nil, "open file \"\(path)\" failed.")
+	// TODO: it physically pains me to write the next lines. Proper error handling is forthcoming.
+	if file == nil {
+		standarderror.write("Error: Opening file \"\(path)\" failed.\n")
+		exit(EXIT_FAILURE)
+	}
+
 	return file!
 }
 
diff --git a/SwiftShellTests/Scripts/exitswhenopeningnon-existentfile.swift b/SwiftShellTests/Scripts/exitswhenopeningnon-existentfile.swift
new file mode 100644
index 0000000..20481d2
--- /dev/null
+++ b/SwiftShellTests/Scripts/exitswhenopeningnon-existentfile.swift
@@ -0,0 +1,5 @@
+
+import SwiftShell
+
+let file = open("file which does not exist")
+print("this is not printed, the script has exited")