#include in C51 retrieves wrong header file

I am designing a project using the Keil C51 V7.50 and
uVision 3 IDE V3.10a on a Silicon Labs C8051F046 MCU. My
project contains source file foo.c, which contains a
directive:

    #include "foo.h"

where foo.h contains standard header info and is located in
the same directory as foo.c.

When I run C51 from the command line, this module compiles
as I expect, but when I compile within uVision 3, it goes
out and finds another foo.h, located in another directory on
the same drive, which is not set up for this project, and
the compile fails.

I can find nothing in the documentation to explain this. I
have checked all the tabs in the "options" dialog box. When
I copy my correct foo.h into the alien directory, uVision 3
will compile it correctly, but I am not content to function
this way.

Any clues why this is happening?

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