diff --git a/lib/src/ast/selector/pseudo.dart b/lib/src/ast/selector/pseudo.dart
index bbf21295c..51e9fed05 100644
--- a/lib/src/ast/selector/pseudo.dart
+++ b/lib/src/ast/selector/pseudo.dart
@@ -170,8 +170,8 @@ class PseudoSelector extends SimpleSelector {
       var minSpecificity = 0;
       var maxSpecificity = 0;
       for (var complex in selector.components) {
-        minSpecificity = math.max(_minSpecificity!, complex.minSpecificity);
-        maxSpecificity = math.max(_maxSpecificity!, complex.maxSpecificity);
+        minSpecificity = math.max(minSpecificity, complex.minSpecificity);
+        maxSpecificity = math.max(maxSpecificity, complex.maxSpecificity);
       }
       _minSpecificity = minSpecificity;
       _maxSpecificity = maxSpecificity;
@@ -180,8 +180,8 @@ class PseudoSelector extends SimpleSelector {
       var minSpecificity = math.pow(super.minSpecificity, 3) as int;
       var maxSpecificity = 0;
       for (var complex in selector.components) {
-        minSpecificity = math.min(_minSpecificity!, complex.minSpecificity);
-        maxSpecificity = math.max(_maxSpecificity!, complex.maxSpecificity);
+        minSpecificity = math.min(minSpecificity, complex.minSpecificity);
+        maxSpecificity = math.max(maxSpecificity, complex.maxSpecificity);
       }
       _minSpecificity = minSpecificity;
       _maxSpecificity = maxSpecificity;
diff --git a/lib/src/exception.dart b/lib/src/exception.dart
index de2ddadb1..1811e0d96 100644
--- a/lib/src/exception.dart
+++ b/lib/src/exception.dart
@@ -99,7 +99,7 @@ class MultiSpanSassException extends SassException
       useColor = true;
     }
 
-    var buffer = StringBuffer("Error: $message");
+    var buffer = StringBuffer("Error: $message\n");
 
     span
         .highlightMultiple(primaryLabel, secondarySpans,
diff --git a/lib/src/extend/extension_store.dart b/lib/src/extend/extension_store.dart
index f0a87cb7c..4f705c130 100644
--- a/lib/src/extend/extension_store.dart
+++ b/lib/src/extend/extension_store.dart
@@ -215,7 +215,7 @@ class ExtensionStore {
 
         for (var simple in component.components) {
           _selectors.putIfAbsent(simple, () => {}).add(selector);
-          if (simple is! PseudoSelector) return;
+          if (simple is! PseudoSelector) continue;
 
           var selectorInPseudo = simple.selector;
           if (selectorInPseudo != null) {
diff --git a/lib/src/extend/functions.dart b/lib/src/extend/functions.dart
index 410aa8739..25bc199ce 100644
--- a/lib/src/extend/functions.dart
+++ b/lib/src/extend/functions.dart
@@ -785,7 +785,7 @@ bool _selectorPseudoIsSuperselector(
       return compound2.components.any((pseudo2) {
         if (pseudo2 is! PseudoSelector) return false;
         if (pseudo2.name != pseudo1.name) return false;
-        if (pseudo2.argument == pseudo1.argument) return false;
+        if (pseudo2.argument != pseudo1.argument) return false;
         var selector2 = pseudo2.selector;
         if (selector2 == null) return false;
         return selector1.isSuperselector(selector2);
diff --git a/lib/src/parse/stylesheet.dart b/lib/src/parse/stylesheet.dart
index 86de0d88f..8dbddf592 100644
--- a/lib/src/parse/stylesheet.dart
+++ b/lib/src/parse/stylesheet.dart
@@ -1200,16 +1200,12 @@ abstract class StylesheetParser extends Parser {
 
     ContentBlock? content;
     if (contentArguments != null || lookingAtChildren()) {
+      var contentArguments_ = contentArguments ??
+          ArgumentDeclaration.empty(span: scanner.emptySpan);
       var wasInContentBlock = _inContentBlock;
       _inContentBlock = true;
-      content = _withChildren(
-          _statement,
-          start,
-          (children, span) => ContentBlock(
-              contentArguments ??
-                  ArgumentDeclaration.empty(span: scanner.emptySpan),
-              children,
-              span));
+      content = _withChildren(_statement, start,
+          (children, span) => ContentBlock(contentArguments_, children, span));
       _inContentBlock = wasInContentBlock;
     } else {
       expectStatementSeparator();
@@ -1724,8 +1720,7 @@ relase. For details, see http://bit.ly/moz-document.
     }
 
     void addSingleExpression(Expression expression, {bool number = false}) {
-      var singleExpression = singleExpression_;
-      if (singleExpression != null) {
+      if (singleExpression_ != null) {
         // If we discover we're parsing a list whose first element is a division
         // operation, and we're in parentheses, reparse outside of a paren
         // context. This ensures that `(1/2 1)` doesn't perform division on its
@@ -1740,7 +1735,10 @@ relase. For details, see http://bit.ly/moz-document.
 
         var spaceExpressions = spaceExpressions_ ??= [];
         resolveOperations();
-        spaceExpressions.add(singleExpression);
+
+        // [singleExpression_] was non-null before, and [resolveOperations]
+        // can't make it null, it can only change it.
+        spaceExpressions.add(singleExpression_!);
         allowSlash = number;
       } else if (!number) {
         allowSlash = false;
@@ -2025,11 +2023,14 @@ relase. For details, see http://bit.ly/moz-document.
           }
 
           var commaExpressions = commaExpressions_ ??= [];
-          var singleExpression = singleExpression_;
-          if (singleExpression == null) scanner.error("Expected expression.");
 
+          if (singleExpression_ == null) scanner.error("Expected expression.");
           resolveSpaceExpressions();
-          commaExpressions.add(singleExpression);
+
+          // [resolveSpaceExpressions can modify [singleExpression_], but it
+          // can't set it to null`.
+          commaExpressions.add(singleExpression_!);
+
           scanner.readChar();
           allowSlash = true;
           singleExpression_ = null;
diff --git a/lib/src/visitor/async_evaluate.dart b/lib/src/visitor/async_evaluate.dart
index 1fe73824a..0cac6b70b 100644
--- a/lib/src/visitor/async_evaluate.dart
+++ b/lib/src/visitor/async_evaluate.dart
@@ -2232,7 +2232,7 @@ class _EvaluateVisitor
                 argument.name,
                 value.withoutSlash(),
                 evaluated.namedNodes.andGet(argument.name) ??
-                    _expressionNode(argument.defaultValue!));
+                    argument.defaultValue.andThen(_expressionNode));
           }
 
           SassArgumentList? argumentList;
diff --git a/lib/src/visitor/evaluate.dart b/lib/src/visitor/evaluate.dart
index 82af67818..3b8bce68a 100644
--- a/lib/src/visitor/evaluate.dart
+++ b/lib/src/visitor/evaluate.dart
@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_evaluate.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: d0e1d0b2e493163e931c957d869473aa57c5b46b
+// Checksum: 01a7ae41ae622e64443597ea82b27b7aeb73d260
 //
 // ignore_for_file: unused_import
 
@@ -2219,7 +2219,7 @@ class _EvaluateVisitor
                 argument.name,
                 value.withoutSlash(),
                 evaluated.namedNodes.andGet(argument.name) ??
-                    _expressionNode(argument.defaultValue!));
+                    argument.defaultValue.andThen(_expressionNode));
           }
 
           SassArgumentList? argumentList;
diff --git a/lib/src/visitor/serialize.dart b/lib/src/visitor/serialize.dart
index 6dc757715..8e0245f9f 100644
--- a/lib/src/visitor/serialize.dart
+++ b/lib/src/visitor/serialize.dart
@@ -390,7 +390,7 @@ class _SerializeVisitor
     }
 
     minimumIndentation =
-        math.min(minimumIndentation, node.value.span.start.column);
+        math.min(minimumIndentation, node.name.span.start.column);
     _writeWithIndent(value, minimumIndentation);
   }