Type `BasePlayer' does not contain a definition for `EnableServerFall'Error

Am i being thick or is this not working anymore

TeamBattlefield - Failed to compile: TeamBattlefield.cs(379,24): error CS1061: Type `BasePlayer' does not contain a definition for `EnableServerFall' and no extension method `EnableServerFall' of type `BasePlayer' could be found. Are you missing an assembly reference?

Also the same error

Error while compiling: TeamBattlefield.cs(379,24): error CS1061: Type `BasePlayer' does not contain a definition for `EnableServerFall' and no extension method `EnableServerFall' of type `BasePlayer' could be found. Are you missing an assembly reference?

Same here

Error while compiling: TeamBattlefield.cs(379,24): error CS1061: Type `BasePlayer' does not contain a definition for `EnableServerFall' and no extension method `EnableServerFall' of type `BasePlayer' could be found. Are you missing an assembly reference?