diff --git a/lib/icinga/dependency-apply.cpp b/lib/icinga/dependency-apply.cpp
index cd4aff3fc..64a700d7e 100644
--- a/lib/icinga/dependency-apply.cpp
+++ b/lib/icinga/dependency-apply.cpp
@@ -112,12 +112,13 @@ bool Dependency::EvaluateApplyRule(const Checkable::Ptr& checkable, const ApplyR
 				BOOST_THROW_EXCEPTION(ScriptError("Array iterator requires value to be an array.", di));
 
 			Dictionary::Ptr dict = vinstances;
+			ObjectLock olock (dict);
 
-			for (const String& key : dict->GetKeys()) {
-				frame.Locals->Set(rule.GetFKVar(), key);
-				frame.Locals->Set(rule.GetFVVar(), dict->Get(key));
+			for (auto& kv : dict) {
+				frame.Locals->Set(rule.GetFKVar(), kv.first);
+				frame.Locals->Set(rule.GetFVVar(), kv.second);
 
-				if (EvaluateApplyRuleInstance(checkable, rule.GetName() + key, frame, rule, skipFilter))
+				if (EvaluateApplyRuleInstance(checkable, rule.GetName() + kv.first, frame, rule, skipFilter))
 					match = true;
 			}
 		}
diff --git a/lib/icinga/notification-apply.cpp b/lib/icinga/notification-apply.cpp
index 51408fb24..24e6f5fbf 100644
--- a/lib/icinga/notification-apply.cpp
+++ b/lib/icinga/notification-apply.cpp
@@ -111,12 +111,13 @@ bool Notification::EvaluateApplyRule(const Checkable::Ptr& checkable, const Appl
 				BOOST_THROW_EXCEPTION(ScriptError("Array iterator requires value to be an array.", di));
 
 			Dictionary::Ptr dict = vinstances;
+			ObjectLock olock (dict);
 
-			for (const String& key : dict->GetKeys()) {
-				frame.Locals->Set(rule.GetFKVar(), key);
-				frame.Locals->Set(rule.GetFVVar(), dict->Get(key));
+			for (auto& kv : dict) {
+				frame.Locals->Set(rule.GetFKVar(), kv.first);
+				frame.Locals->Set(rule.GetFVVar(), kv.second);
 
-				if (EvaluateApplyRuleInstance(checkable, rule.GetName() + key, frame, rule, skipFilter))
+				if (EvaluateApplyRuleInstance(checkable, rule.GetName() + kv.first, frame, rule, skipFilter))
 					match = true;
 			}
 		}
diff --git a/lib/icinga/scheduleddowntime-apply.cpp b/lib/icinga/scheduleddowntime-apply.cpp
index 7aea69ebf..558dcfd86 100644
--- a/lib/icinga/scheduleddowntime-apply.cpp
+++ b/lib/icinga/scheduleddowntime-apply.cpp
@@ -110,12 +110,13 @@ bool ScheduledDowntime::EvaluateApplyRule(const Checkable::Ptr& checkable, const
 				BOOST_THROW_EXCEPTION(ScriptError("Array iterator requires value to be an array.", di));
 
 			Dictionary::Ptr dict = vinstances;
+			ObjectLock olock (dict);
 
-			for (const String& key : dict->GetKeys()) {
-				frame.Locals->Set(rule.GetFKVar(), key);
-				frame.Locals->Set(rule.GetFVVar(), dict->Get(key));
+			for (auto& kv : dict) {
+				frame.Locals->Set(rule.GetFKVar(), kv.first);
+				frame.Locals->Set(rule.GetFVVar(), kv.second);
 
-				if (EvaluateApplyRuleInstance(checkable, rule.GetName() + key, frame, rule, skipFilter))
+				if (EvaluateApplyRuleInstance(checkable, rule.GetName() + kv.first, frame, rule, skipFilter))
 					match = true;
 			}
 		}
diff --git a/lib/icinga/service-apply.cpp b/lib/icinga/service-apply.cpp
index d6d6c1b35..ab472a47a 100644
--- a/lib/icinga/service-apply.cpp
+++ b/lib/icinga/service-apply.cpp
@@ -101,12 +101,13 @@ bool Service::EvaluateApplyRule(const Host::Ptr& host, const ApplyRule& rule, bo
 				BOOST_THROW_EXCEPTION(ScriptError("Array iterator requires value to be an array.", di));
 
 			Dictionary::Ptr dict = vinstances;
+			ObjectLock olock (dict);
 
-			for (const String& key : dict->GetKeys()) {
-				frame.Locals->Set(rule.GetFKVar(), key);
-				frame.Locals->Set(rule.GetFVVar(), dict->Get(key));
+			for (auto& kv : dict) {
+				frame.Locals->Set(rule.GetFKVar(), kv.first);
+				frame.Locals->Set(rule.GetFVVar(), kv.second);
 
-				if (EvaluateApplyRuleInstance(host, rule.GetName() + key, frame, rule, skipFilter))
+				if (EvaluateApplyRuleInstance(host, rule.GetName() + kv.first, frame, rule, skipFilter))
 					match = true;
 			}
 		}