diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 21d391b80..987ad1177 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -1835,7 +1835,7 @@ void TypeChecker::endVisit(BinaryOperation const& _operation)
 			*userDefinedFunctionType->parameterTypes().at(0) ==
 			*userDefinedFunctionType->parameterTypes().at(1)
 		);
-		commonType = userDefinedFunctionType->parameterTypes().at(0);
+		commonType = userDefinedFunctionType->returnParameterTypes().at(0);
 	}
 
 	_operation.annotation().commonType = commonType;
diff --git a/libsolidity/codegen/ir/IRGeneratorForStatements.cpp b/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
index 6bcd6ab9c..61e70f257 100644
--- a/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
+++ b/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
@@ -775,7 +775,7 @@ bool IRGeneratorForStatements::visit(BinaryOperation const& _binOp)
 {
 	setLocation(_binOp);
 
-	// TOOD make this nicer
+	// TODO: make this nicer
 	if (_binOp.annotation().userDefinedFunction)
 	{
 		_binOp.leftExpression().accept(*this);
diff --git a/libsolidity/parsing/Parser.cpp b/libsolidity/parsing/Parser.cpp
index 6f71de48c..b1569fa76 100644
--- a/libsolidity/parsing/Parser.cpp
+++ b/libsolidity/parsing/Parser.cpp
@@ -990,7 +990,7 @@ ASTPointer<UsingForDirective> Parser::parseUsingDirective()
 				};
 				if (!util::contains(overridable, operator_))
 					parserError(
-						1885_error,
+						4403_error,
 						("The operator " + string{TokenTraits::toString(operator_)} + " cannot be user-implemented. This is only possible for the following operators: ") +
 						util::joinHumanReadable(overridable | ranges::views::transform([](Token _t) { return string{TokenTraits::toString(_t)}; }))
 					);
diff --git a/test/libsolidity/syntaxTests/operators/custom/operator_not_user_implemented.sol b/test/libsolidity/syntaxTests/operators/custom/operator_not_user_implemented.sol
index e5db8ee7d..499b3c5af 100644
--- a/test/libsolidity/syntaxTests/operators/custom/operator_not_user_implemented.sol
+++ b/test/libsolidity/syntaxTests/operators/custom/operator_not_user_implemented.sol
@@ -4,7 +4,7 @@ using {
 } for int256;
 
 // ----
-// ParserError 1885: (22-24): The operator << cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
-// ParserError 1885: (36-38): The operator >> cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
-// ParserError 1885: (51-53): The operator ** cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
-// ParserError 1885: (62-63): The operator ! cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
+// ParserError 4403: (22-24): The operator << cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
+// ParserError 4403: (36-38): The operator >> cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
+// ParserError 4403: (51-53): The operator ** cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~
+// ParserError 4403: (62-63): The operator ! cannot be user-implemented. This is only possible for the following operators: |, &, ^, +, -, *, /, %, ==, !=, <, >, <=, >=, ~