Corruption of program stacks is detected by using guard words placed in the program stacks. A called routine or module executing on a processor checks a guard word in a stack frame of a calling routine or module. 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 modules, however, may not support use of guard words. Thus, modules that are interlinked may have differing protection capabilities. A determination is made as to the differing protection capabilities, an indication of the same is provided and the modules are executed with failing due to the differing protection capabilities.