diff --git a/api/core/app/apps/base_app_generator.py b/api/core/app/apps/base_app_generator.py
index 6e6da95401..3325e30088 100644
--- a/api/core/app/apps/base_app_generator.py
+++ b/api/core/app/apps/base_app_generator.py
@@ -91,6 +91,9 @@ class BaseAppGenerator:
             )
 
         if variable_entity.type == VariableEntityType.NUMBER and isinstance(value, str):
+            # handle empty string case
+            if not value.strip():
+                return None
             # may raise ValueError if user_input_value is not a valid number
             try:
                 if "." in value: