diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index c613dd796d98..5449631a26ec 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -2348,7 +2348,16 @@ void TypeChecker::typeCheckStringConcatFunction(
 {
 	solAssert(_functionType);
 	solAssert(_functionType->kind() == FunctionType::Kind::StringConcat);
-	solAssert(_functionCall.names().empty());
+
+	if (!_functionCall.names().empty())
+	{
+		m_errorReporter.typeError(
+			4903_error,
+			_functionCall.location(),
+			"Named arguments cannot be used with string.concat()."
+		);
+		return;
+	}
 
 	typeCheckFunctionGeneralChecks(_functionCall, _functionType);
 
@@ -2375,7 +2384,16 @@ void TypeChecker::typeCheckBytesConcatFunction(
 {
 	solAssert(_functionType);
 	solAssert(_functionType->kind() == FunctionType::Kind::BytesConcat);
-	solAssert(_functionCall.names().empty());
+
+	if (!_functionCall.names().empty())
+	{
+		m_errorReporter.typeError(
+			8145_error,
+			_functionCall.location(),
+			"Named arguments cannot be used with bytes.concat()."
+		);
+		return;
+	}
 
 	typeCheckFunctionGeneralChecks(_functionCall, _functionType);
 
diff --git a/test/libsolidity/syntaxTests/array/concat/bytes_concat_named_args.sol b/test/libsolidity/syntaxTests/array/concat/bytes_concat_named_args.sol
new file mode 100644
index 000000000000..7288a054fa37
--- /dev/null
+++ b/test/libsolidity/syntaxTests/array/concat/bytes_concat_named_args.sol
@@ -0,0 +1,7 @@
+contract C {
+    function f() public pure {
+        bytes.concat({x: "abc", y: hex"00"});
+    }
+}
+// ----
+// TypeError 8145: (52-88): Named arguments cannot be used with bytes.concat().
diff --git a/test/libsolidity/syntaxTests/string/concat/string_concat_named_args.sol b/test/libsolidity/syntaxTests/string/concat/string_concat_named_args.sol
new file mode 100644
index 000000000000..48e50826bc95
--- /dev/null
+++ b/test/libsolidity/syntaxTests/string/concat/string_concat_named_args.sol
@@ -0,0 +1,7 @@
+contract C {
+    function f() public pure {
+        string.concat({x: "abc", y: "def"});
+    }
+}
+// ----
+// TypeError 4903: (52-87): Named arguments cannot be used with string.concat().