diff --git a/src/libslic3r/Config.cpp b/src/libslic3r/Config.cpp
index 208a041d2..75f882161 100644
--- a/src/libslic3r/Config.cpp
+++ b/src/libslic3r/Config.cpp
@@ -735,25 +735,25 @@ double ConfigBase::get_computed_value(const t_config_option_key &opt_key, int ex
         }
         if (idx >= 0) {
             if (raw_opt->type() == coFloats || raw_opt->type() == coInts || raw_opt->type() == coBools)
-                return vector_opt->getFloat(extruder_id);
+                return vector_opt->getFloat(idx);
             if (raw_opt->type() == coFloatsOrPercents) {
                 const ConfigOptionFloatsOrPercents* opt_fl_per = static_cast<const ConfigOptionFloatsOrPercents*>(raw_opt);
-                if (!opt_fl_per->values[extruder_id].percent)
-                    return opt_fl_per->values[extruder_id].value;
+                if (!opt_fl_per->values[idx].percent)
+                    return opt_fl_per->values[idx].value;
 
                 if (opt_def->ratio_over.empty())
-                    return opt_fl_per->get_abs_value(extruder_id, 1);
+                    return opt_fl_per->get_abs_value(idx, 1);
                 if (opt_def->ratio_over != "depends")
-                    return opt_fl_per->get_abs_value(extruder_id, this->get_computed_value(opt_def->ratio_over, extruder_id));
+                    return opt_fl_per->get_abs_value(idx, this->get_computed_value(opt_def->ratio_over, idx));
                 std::stringstream ss; ss << "ConfigBase::get_abs_value(): " << opt_key << " has no valid ratio_over to compute of";
                 throw ConfigurationError(ss.str());
             }
             if (raw_opt->type() == coPercents) {
                 const ConfigOptionPercents* opt_per = static_cast<const ConfigOptionPercents*>(raw_opt);
                 if (opt_def->ratio_over.empty())
-                    return opt_per->get_abs_value(extruder_id, 1);
+                    return opt_per->get_abs_value(idx, 1);
                 if (opt_def->ratio_over != "depends")
-                    return opt_per->get_abs_value(extruder_id, this->get_computed_value(opt_def->ratio_over, extruder_id));
+                    return opt_per->get_abs_value(idx, this->get_computed_value(opt_def->ratio_over, idx));
                 std::stringstream ss; ss << "ConfigBase::get_abs_value(): " << opt_key << " has no valid ratio_over to compute of";
                 throw ConfigurationError(ss.str());
             }
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index a5f9e23a9..e69d584e4 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -659,10 +659,10 @@ void PrintConfigDef::init_fff_params()
     def->full_label = L("Default acceleration");
     def->tooltip = L("This is the acceleration your printer will be reset to after "
                    "the role-specific acceleration values are used (perimeter/infill). "
-                   "\nYou can set it as a % of the max of the X/Y machine acceleration limit."
+                   "\nYou can set it as a % of the max of the X machine acceleration limit."
                    "\nSet zero to prevent resetting acceleration at all.");
     def->sidetext = L("mm/s² or %");
-    def->ratio_over = "machine_max_acceleration_X";
+    def->ratio_over = "machine_max_acceleration_x";
     def->min = 0;
     def->max_literal = { -200, false };
     def->mode = comExpert;