diff --git a/lib/icinga/apiactions.cpp b/lib/icinga/apiactions.cpp
index bda0e336b..ff3c6506d 100644
--- a/lib/icinga/apiactions.cpp
+++ b/lib/icinga/apiactions.cpp
@@ -55,6 +55,8 @@ Dictionary::Ptr ApiActions::CreateResult(int code, const String& status,
 Dictionary::Ptr ApiActions::ProcessCheckResult(const ConfigObject::Ptr& object,
 	const Dictionary::Ptr& params)
 {
+	using Result = Checkable::ProcessingResult;
+
 	Checkable::Ptr checkable = static_pointer_cast<Checkable>(object);
 
 	if (!checkable)
@@ -123,9 +125,19 @@ Dictionary::Ptr ApiActions::ProcessCheckResult(const ConfigObject::Ptr& object,
 	if (params->Contains("ttl"))
 		cr->SetTtl(HttpUtility::GetLastParameter(params, "ttl"));
 
-	checkable->ProcessCheckResult(cr);
+	Result result = checkable->ProcessCheckResult(cr);
+	switch (result) {
+		case Result::Ok:
+			return ApiActions::CreateResult(200, "Successfully processed check result for object '" + checkable->GetName() + "'.");
+		case Result::NoCheckResult:
+			return ApiActions::CreateResult(400, "Could not process check result for object '" + checkable->GetName() + "' because no check result was passed.");
+		case Result::CheckableInactive:
+			return ApiActions::CreateResult(503, "Could not process check result for object '" + checkable->GetName() + "' because the object is inactive.");
+		case Result::NewerCheckResultPresent:
+			return ApiActions::CreateResult(409, "Newer check result already present. Check result for '" + checkable->GetName() + "' was discarded.");
+	}
 
-	return ApiActions::CreateResult(200, "Successfully processed check result for object '" + checkable->GetName() + "'.");
+	return ApiActions::CreateResult(500, "Unexpected result (" + std::to_string(static_cast<int>(result)) + ") for object '" + checkable->GetName() + "'. Please submit a bug report at https://github.com/Icinga/icinga2");
 }
 
 Dictionary::Ptr ApiActions::RescheduleCheck(const ConfigObject::Ptr& object,
diff --git a/lib/icinga/checkable-check.cpp b/lib/icinga/checkable-check.cpp
index a302bd923..921231a9e 100644
--- a/lib/icinga/checkable-check.cpp
+++ b/lib/icinga/checkable-check.cpp
@@ -94,15 +94,17 @@ double Checkable::GetLastCheck() const
 	return schedule_end;
 }
 
-void Checkable::ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrigin::Ptr& origin)
+Checkable::ProcessingResult Checkable::ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrigin::Ptr& origin)
 {
+	using Result = Checkable::ProcessingResult;
+
 	{
 		ObjectLock olock(this);
 		m_CheckRunning = false;
 	}
 
 	if (!cr)
-		return;
+		return Result::NoCheckResult;
 
 	double now = Utility::GetTime();
 
@@ -142,12 +144,12 @@ void Checkable::ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrig
 			listener->SyncSendMessage(command_endpoint, message);
 		}
 
-		return;
+		return Result::Ok;
 
 	}
 
 	if (!IsActive())
-		return;
+		return Result::CheckableInactive;
 
 	bool reachable = IsReachable();
 	bool notification_reachable = IsReachable(DependencyNotification);
@@ -184,7 +186,7 @@ void Checkable::ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrig
 					<< Utility::FormatDateTime("%Y-%m-%d %H:%M:%S %z", newCRTimestamp) << " (" << newCRTimestamp
 					<< "). It is in the past compared to ours at "
 					<< Utility::FormatDateTime("%Y-%m-%d %H:%M:%S %z", currentCRTimestamp) << " (" << currentCRTimestamp << ").";
-				return;
+				return Result::NewerCheckResultPresent;
 			}
 		}
 	}
@@ -526,6 +528,8 @@ void Checkable::ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrig
 	/* update reachability for child objects */
 	if ((stateChange || hardChange) && !children.empty())
 		OnReachabilityChanged(this, cr, children, origin);
+
+	return Result::Ok;
 }
 
 void Checkable::ExecuteRemoteCheck(const Dictionary::Ptr& resolvedMacros)
diff --git a/lib/icinga/checkable.hpp b/lib/icinga/checkable.hpp
index bb8e567b4..6a46425a9 100644
--- a/lib/icinga/checkable.hpp
+++ b/lib/icinga/checkable.hpp
@@ -111,7 +111,14 @@ public:
 
 	void ExecuteRemoteCheck(const Dictionary::Ptr& resolvedMacros = nullptr);
 	void ExecuteCheck();
-	void ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrigin::Ptr& origin = nullptr);
+	enum class ProcessingResult
+	{
+		Ok,
+		NoCheckResult,
+		CheckableInactive,
+		NewerCheckResultPresent,
+	};
+	ProcessingResult ProcessCheckResult(const CheckResult::Ptr& cr, const MessageOrigin::Ptr& origin = nullptr);
 
 	Endpoint::Ptr GetCommandEndpoint() const;