PLS-320: the declaration of the type of this expression is incomplete or malformed

I was recently helping a colleague troubleshot an odd Oracle error in a pl/sql block he was writing. The error he received was:
ORA-06553: PLS-320: the declaration of the type of this expression is incomplete or malformed
ORA-06550: line 3, column 123
And of course, line 3 held nothing interesting in relation to the error.

After looking for a long while I found out the problem only occurred when the cursor was selecting from a particular table. The database structure was an off the shelf product that stored images as blobs. The issue ended up being that the developer creatively named the column “BLOB” as it was the datatype. After all, how else would someone looking at the table know what the column held?

Oracle support classifies it as bug 6331062 and it seems to affect many different versions/platforms.

The moral of the story: think before you name your columns.