It is shown that, contrary to recent suggestions, the exponent ν, characterizing self-avoiding walks in a diluted lattice at the percolation threshold is determined by a fixed point, different from the pure-lattice one. The full phase diagram of this system is obtained by a real-space renormalization-group treatment and five nontrivial fixed points are identified. A field-theoretical treatment yields ν=1/2+ε/42, with ε=6-d. All these results are supported by exact enumeration analysis.