CS not correctly assumed

A near CALL or JMP instruction can't have as its target an address in a
different segment. For example,

   SEG1  SEGMENT
   LAB1  LABEL NEAR 
   SEG1  ENDS 
   SEG2  SEGMENT 
      jmp LAB1        ;error, wrong segment 
   SEG2  ENDS 

This error only occurs in MASM mode. Ideal mode correctly handles this
situation.