The present invention refers to a pen cap (10), being capable of covering a distal end of a drug delivery device comprising at least one protruding element (16, 18, 36) located inside the pen cap (10) which prevents that the rim of an outer needle cap (14), while being a protective casing for the needle at the distal end of the drug delivery device, can get stuck within a part of the pen cap (10) if the user puts the pen cap (10) on the drug delivery device. The inner diameter of the pen cap (10) is reduced by means of the at least one protruding element (16, 18, 36), such that the inner diameter of the pen cap (10) is smaller than the largest outer diameter (26) of the outer needle cap (20). Furthermore, the invention relates to a drug delivery device comprising a pen cap (10) with the described protruding elements (16, 18, 36). Significant Figure: Fig. 1
