diff --git a/cdoc/Lock.cpp b/cdoc/Lock.cpp
index ce9f9079..5014d2fe 100644
--- a/cdoc/Lock.cpp
+++ b/cdoc/Lock.cpp
@@ -30,18 +30,23 @@ namespace libcdoc {
 std::string
 Lock::getString(Params key) const
 {
-    const std::vector<uint8_t>& bytes = params.at(key);
-    return {(const char *) bytes.data(), bytes.size()};
+    if (params.contains(key)) {
+        const std::vector<uint8_t>& bytes = params.at(key);
+        return {(const char *) bytes.data(), bytes.size()};
+    }
+    return {};
 }
 
 int32_t
 Lock::getInt(Params key) const
 {
-	const std::vector<uint8_t>& bytes = params.at(key);
 	int32_t val = 0;
-	for (int i = 0; (i < bytes.size()) && (i < 4); i++) {
-		val = (val << 8) | bytes.at(i);
-	}
+    if (params.contains(key)) {
+        const std::vector<uint8_t>& bytes = params.at(key);
+        for (int i = 0; (i < bytes.size()) && (i < 4); i++) {
+            val = (val << 8) | bytes.at(i);
+        }
+    }
 	return val;
 }