Corollary 2
Tag 0BAH, permanent. Cite it as [Bourbaki, Tag 0BAH].
General Topology, chapter I, § 10. Proper mappings
Every continuous mapping of a quasi-compact space into a Hausdorff space is proper.
The composition is proper by Corollary 1; hence is proper by no. 1, Proposition 5 d). Alternatively we may apply the criterion b) of Theorem 1, using § 9, no. 4, Theorem 2, Corollary 2.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.