The D.I was fitted with various armaments. It was initially armed with a single Schwarzlose machine gun, which was mounted onto braces set into the upper fuselage; this arrangement was clear of the propeller blades yet still allowed for easy in-flight access to the breach mechanism. Ammunition was stored in a drum within the fuselage decking and belt-fed to the gun via a purpose-built conduit. However, this arrangement was commonly judged to have been outmoded by the time that the D.I was entering service; accordingly, a new armament arrange was soon adopted. A twin Schewarzlose gun arrangement, which featured synchronization gear as to allow the rounds to pass directly between the propeller blades without striking them; however, the locally produced interrupter mechanism was found to be unreliable in service when the engine was ran at certain speeds. In spite of the issue, which made the guns prone to striking the propeller blades, this newer armament arrangement was rolled out. Further changes, including the guns being set further back, were also made late on into production.