Forum Discussion
Dataflow Gen2 MashupException.Error We cannot convert the value null to type Number
Hi v-kpoloju-msft, rohit1991 and collinq. I found the solution! The issue was with a table I was merging into another. The key was a number, but in one of the tables, the service converted it to text. As a result, the merge returned only null values. When I performed operations on that merged column, the error occurred.
The strangest part is that, in the dataflow preview, the column appeared to merge correctly, making it seem like everything was working correctly. It wasn't until I created another dataflow referencing a pared-down version of the first one that the errors became visible in the preview. Thanks again for everyone reaching out!
Super UserHi data_4_good
This error usually means Power Query is trying to convert a column to a number type but hits unexpected nulls or text values during staging.
Instead of just replacing nulls, also check if the merge introduced unexpected text in a numeric column. That’s a common issue—especially if two tables have different data types for the same key.
You can also wrap the conversion using try Number.From(...) otherwise null in Power Query to prevent it from breaking. It handles type mismatches more safely.