diff --git a/src/preferences/credentials.cpp b/src/preferences/credentials.cpp
index c8024830b6c9..8bfbcbf43e88 100644
--- a/src/preferences/credentials.cpp
+++ b/src/preferences/credentials.cpp
@@ -278,7 +278,7 @@ secure_buffer encrypt(const secure_buffer& text, const secure_buffer& key)
 secure_buffer decrypt(const secure_buffer& text, const secure_buffer& key)
 {
 	auto buf = rc4_crypt(text, key);
-	while(buf.back() == 0) {
+	while(!buf.empty() && buf.back() == 0) {
 		buf.pop_back();
 	}
 	return buf;