Corruption of program stacks is detected by using guard words placed in the program stacks. A called routine executing on a processor checks a guard word in a stack frame of a calling routine. The checking determines whether the guard word has an expected value. Based on determining the guard word has an unexpected value, an indication of corruption of the stack frame is provided. Some routines, however, may not support use of guard words. Thus, routines that are interlinked may have differing protection capabilities. In this situation, a determination may be made as to whether a caller routine supports guard word protection. Based on determining that the caller routine supports guard word protection, the called routine verifies the guard word.