diff --git a/internal/config/parameter.go b/internal/config/parameter.go
index 4037ee6..757a09e 100644
--- a/internal/config/parameter.go
+++ b/internal/config/parameter.go
@@ -20,5 +20,19 @@ func (param *Parameter) Validate(datatypes ...datatype.T) error {
 		param.Type = param.Type[1:]
 	}
 
+	// assign the datatype
+	datatypeFound := false
+	for _, dtype := range datatypes {
+		param.Validator = dtype.Build(param.Type, datatypes...)
+		if param.Validator != nil {
+			datatypeFound = true
+			param.ExtractType = dtype.Type()
+			break
+		}
+	}
+	if !datatypeFound {
+		return ErrUnknownDataType
+	}
+
 	return nil
 }
diff --git a/internal/config/service.go b/internal/config/service.go
index 7c20724..224de81 100644
--- a/internal/config/service.go
+++ b/internal/config/service.go
@@ -222,7 +222,7 @@ func (svc *Service) validateInput(types []datatype.T) error {
 			param.Rename = paramName
 		}
 
-		err := param.Validate()
+		err := param.Validate(types...)
 		if err != nil {
 			return fmt.Errorf("%s: %w", paramName, err)
 		}
@@ -232,21 +232,7 @@ func (svc *Service) validateInput(types []datatype.T) error {
 			return fmt.Errorf("%s: %w", paramName, ErrIllegalOptionalURIParam)
 		}
 
-		// assign the datatype
-		datatypeFound := false
-		for _, dtype := range types {
-			param.Validator = dtype.Build(param.Type, types...)
-			if param.Validator != nil {
-				datatypeFound = true
-				param.ExtractType = dtype.Type()
-				break
-			}
-		}
-		if !datatypeFound {
-			return fmt.Errorf("%s: %w", paramName, ErrUnknownDataType)
-		}
-
-		// check for name/rename conflict
+		// fail on name/rename conflict
 		for paramName2, param2 := range svc.Input {
 			// ignore self
 			if paramName == paramName2 {