diff --git a/packages/editor-ui/src/components/ParameterInput.vue b/packages/editor-ui/src/components/ParameterInput.vue
index 74c123b52..9f65d462e 100644
--- a/packages/editor-ui/src/components/ParameterInput.vue
+++ b/packages/editor-ui/src/components/ParameterInput.vue
@@ -276,7 +276,7 @@ export default mixins(
 					returnValue = this.expressionValueComputed;
 				}
 
-				if (returnValue !== undefined && this.parameter.type === 'string') {
+				if (returnValue !== undefined && returnValue !== null && this.parameter.type === 'string') {
 					const rows = this.getArgument('rows');
 					if (rows === undefined || rows === 1) {
 						returnValue = returnValue.toString().replace(/\n/, '|');
diff --git a/packages/workflow/src/Workflow.ts b/packages/workflow/src/Workflow.ts
index 9bb8391ae..45854ce97 100644
--- a/packages/workflow/src/Workflow.ts
+++ b/packages/workflow/src/Workflow.ts
@@ -890,16 +890,16 @@ export class Workflow {
 		// Execute the expression
 		try {
 			const returnValue = tmpl.tmpl(parameterValue, dataProxy.getDataProxy());
-			if (typeof returnValue === 'object' && Object.keys(returnValue).length === 0) {
-				// When expression is incomplete it returns a Proxy which causes problems.
-				// Catch it with this code and return a proper error.
-				throw new Error('Expression is not valid.');
+			if (returnValue !== null && typeof returnValue === 'object') {
+				if (Object.keys(returnValue).length === 0) {
+					// When expression is incomplete it returns a Proxy which causes problems.
+					// Catch it with this code and return a proper error.
+					throw new Error('Expression is not valid.');
+				}
+				if (returnObjectAsString === true)  {
+					return this.convertObjectValueToString(returnValue);
+				}
 			}
-
-			if (returnObjectAsString === true && typeof returnValue === 'object') {
-				return this.convertObjectValueToString(returnValue);
-			}
-
 			return returnValue;
 		} catch (e) {
 			throw new Error('Expression is not valid.');