diff --git a/src/fn_selectors.cpp b/src/fn_selectors.cpp
index eb2e1382b5..34142bb81c 100644
--- a/src/fn_selectors.cpp
+++ b/src/fn_selectors.cpp
@@ -16,18 +16,21 @@ namespace Sass {
       List* arglist = ARG("$selectors", List);
 
       // Not enough parameters
-      if( arglist->length() == 0 )
-        error("$selectors: At least one selector must be passed for `selector-nest'", pstate, traces);
+      if (arglist->length() == 0) {
+        error(
+          "$selectors: At least one selector must be passed for `selector-nest'",
+          pstate, traces);
+      }
 
       // Parse args into vector of selectors
       SelectorStack parsedSelectors;
       for (size_t i = 0, L = arglist->length(); i < L; ++i) {
         Expression_Obj exp = Cast<Expression>(arglist->value_at_index(i));
         if (exp->concrete_type() == Expression::NULL_VAL) {
-          std::stringstream msg;
-          msg << "$selectors: null is not a valid selector: it must be a string,\n";
-          msg << "a list of strings, or a list of lists of strings for 'selector-nest'";
-          error(msg.str(), pstate, traces);
+          error(
+            "$selectors: null is not a valid selector: it must be a string,\n"
+            "a list of strings, or a list of lists of strings for 'selector-nest'",
+            pstate, traces);
         }
         if (String_Constant_Obj str = Cast<String_Constant>(exp)) {
           str->quote_mark(0);
@@ -42,23 +45,18 @@ namespace Sass {
         return SASS_MEMORY_NEW(Null, pstate);
       }
 
-      // Set the first element as the `result`, keep appending to as we go down the parsedSelector vector.
+      // Set the first element as the `result`, keep
+      // appending to as we go down the parsedSelector vector.
       SelectorStack::iterator itr = parsedSelectors.begin();
-      SelectorListObj result = *itr;
+      SelectorListObj& result = *itr;
       ++itr;
 
       for(;itr != parsedSelectors.end(); ++itr) {
-        SelectorListObj child = *itr;
-        std::vector<ComplexSelectorObj> exploded;
-        selector_stack.push_back(result);
+        SelectorListObj& child = *itr;
         original_stack.push_back(result);
         SelectorListObj rv = child->resolve_parent_refs(original_stack, traces);
-        selector_stack.pop_back();
+        result->elements(rv->elements());
         original_stack.pop_back();
-        for (size_t m = 0, mLen = rv->length(); m < mLen; ++m) {
-          exploded.push_back((*rv)[m]);
-        }
-        result->elements(exploded);
       }
 
       return Cast<Value>(Listize::perform(result));
@@ -71,34 +69,36 @@ namespace Sass {
 
       // Not enough parameters
       if (arglist->empty()) {
-        error("$selectors: At least one selector must be "
-          "passed for `selector-append'", pstate, traces);
+        error(
+          "$selectors: At least one selector must be "
+          "passed for `selector-append'",
+          pstate, traces);
       }
 
       // Parse args into vector of selectors
       SelectorStack parsedSelectors;
       parsedSelectors.push_back({});
       for (size_t i = 0, L = arglist->length(); i < L; ++i) {
-        Expression_Obj exp = Cast<Expression>(arglist->value_at_index(i));
+        Expression* exp = Cast<Expression>(arglist->value_at_index(i));
         if (exp->concrete_type() == Expression::NULL_VAL) {
-          std::stringstream msg;
-          msg << "$selectors: null is not a valid selector: it must be a string,\n";
-          msg << "a list of strings, or a list of lists of strings for 'selector-append'";
-          error(msg.str(), pstate, traces);
+          error(
+            "$selectors: null is not a valid selector: it must be a string,\n"
+             "a list of strings, or a list of lists of strings for 'selector-append'",
+            pstate, traces);
         }
         if (String_Constant* str = Cast<String_Constant>(exp)) {
           str->quote_mark(0);
         }
         std::string exp_src = exp->to_string();
         SelectorListObj sel = Parser::parse_selector(exp_src.c_str(), ctx, traces,
-                                                       exp->pstate(), pstate.src,
-                                                       /*allow_parent=*/true);
+                                                     exp->pstate(), pstate.src,
+                                                     /*allow_parent=*/true);
 
-        for (auto complex : sel->elements()) {
+        for (auto& complex : sel->elements()) {
           if (complex->empty()) {
             complex->append(SASS_MEMORY_NEW(CompoundSelector, "[phony]"));
           }
-          if (CompoundSelectorObj comp = Cast<CompoundSelector>(complex->first())) {
+          if (CompoundSelector* comp = Cast<CompoundSelector>(complex->first())) {
             comp->hasRealParent(true);
             complex->chroots(true);
           }
@@ -108,13 +108,14 @@ namespace Sass {
 
           if (!sel->has_real_parent_ref()) {
             auto parent = parsedSelectors.back();
-            for (auto complex : parent->elements()) {
-              if (CompoundSelectorObj comp = Cast<CompoundSelector>(complex->first())) {
+            for (auto& complex : parent->elements()) {
+              if (CompoundSelector* comp = Cast<CompoundSelector>(complex->first())) {
                 comp->hasRealParent(false);
               }
             }
             error("Can't append \"" + sel->to_string() + "\" to \"" +
-            parent->to_string() + "\" for `selector-append'", pstate, traces);
+              parent->to_string() + "\" for `selector-append'",
+              pstate, traces);
           }
 
           // Build the resolved stack from the left. It's cheaper to directly
@@ -155,7 +156,7 @@ namespace Sass {
       List* l = SASS_MEMORY_NEW(List, sel->pstate(), sel->length(), SASS_COMMA);
 
       for (size_t i = 0, L = sel->length(); i < L; ++i) {
-        SimpleSelectorObj ss = (*sel)[i];
+        const SimpleSelectorObj& ss = sel->get(i);
         std::string ss_string = ss->to_string() ;
         l->append(SASS_MEMORY_NEW(String_Quoted, ss->pstate(), ss_string));
       }