Strange behavior with the ":block/content" attribute when building Advanced Queries

I’m very new to Datalog and writing Advanced Queries, so apologies if this is an obvious mistake, but I can’t seem to find a clear answer after looking through this forum and Googling around.

If I create the following query, it seems to do what I’d expect it to do, which is show every block with a “:block/marker” attribute.

{:query [:find (pull ?b [*])
       [?b :block/marker]

But if I do the same query using the attribute “:block/content”, rather than show all the blocks with a “:block/content” attribute, I just get an error. Does anyone have an idea as to why that is?