diff --git a/lib/base/value-operators.cpp b/lib/base/value-operators.cpp
index 554c96dba..9b39c1e2f 100644
--- a/lib/base/value-operators.cpp
+++ b/lib/base/value-operators.cpp
@@ -202,7 +202,9 @@ Value icinga::operator+(const String& lhs, const Value& rhs)
 
 Value icinga::operator+(const Value& lhs, const Value& rhs)
 {
-	if ((lhs.IsString() || lhs.IsEmpty()) && (rhs.IsString() || rhs.IsEmpty()) && !(lhs.IsEmpty() && rhs.IsEmpty()))
+	if ((lhs.IsEmpty() || lhs.IsNumber()) && (rhs.IsEmpty() || rhs.IsNumber()) && !(lhs.IsEmpty() && rhs.IsEmpty()))
+		return static_cast<double>(lhs) + static_cast<double>(rhs);
+	if ((lhs.IsString() || lhs.IsEmpty() || lhs.IsNumber()) && (rhs.IsString() || rhs.IsEmpty() || rhs.IsNumber()) && !(lhs.IsEmpty() && rhs.IsEmpty()))
 		return static_cast<String>(lhs) + static_cast<String>(rhs);
 	else if ((lhs.IsNumber() || lhs.IsEmpty()) && (rhs.IsNumber() || rhs.IsEmpty()) && !(lhs.IsEmpty() && rhs.IsEmpty()))
 		return static_cast<double>(lhs) + static_cast<double>(rhs);
diff --git a/test/config-ops.cpp b/test/config-ops.cpp
index db3d44806..388630e2c 100644
--- a/test/config-ops.cpp
+++ b/test/config-ops.cpp
@@ -183,6 +183,18 @@ BOOST_AUTO_TEST_CASE(simple)
 	expr = ConfigCompiler::CompileText("<test>", "test");
 	BOOST_CHECK_THROW(expr->Evaluate(frame), ConfigError);
 	delete expr;
+
+	expr = ConfigCompiler::CompileText("<test>", "null + 3");
+	BOOST_CHECK(expr->Evaluate(frame) == 3);
+	delete expr;
+
+	expr = ConfigCompiler::CompileText("<test>", "3 + null");
+	BOOST_CHECK(expr->Evaluate(frame) == 3);
+	delete expr;
+
+	expr = ConfigCompiler::CompileText("<test>", "\"test\" + 3");
+	BOOST_CHECK(expr->Evaluate(frame) == "test3");
+	delete expr;
 }
 
 BOOST_AUTO_TEST_CASE(advanced)