diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java b/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java
index 3eb63a06124..fdff83d539e 100644
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/parser/JavacParser.java
@@ -4039,7 +4039,7 @@ public class JavacParser implements Parser {
             }
         }
 
-        int primaryPos = defs.first().pos;
+        int primaryPos = getStartPos(defs.first());
         String simplename = PathFileObject.getSimpleName(log.currentSourceFile());
 
         if (simplename.endsWith(".java")) {
@@ -4050,7 +4050,7 @@ public class JavacParser implements Parser {
         }
 
         Name name = names.fromString(simplename);
-        JCModifiers unnamedMods = F.at(primaryPos)
+        JCModifiers unnamedMods = F.at(Position.NOPOS)
                 .Modifiers(Flags.FINAL|Flags.SYNTHETIC|Flags.UNNAMED_CLASS, List.nil());
         JCClassDecl unnamed = F.at(primaryPos).ClassDef(
                 unnamedMods, name, List.nil(), null, List.nil(), List.nil(),
diff --git a/test/langtools/tools/javac/parser/JavacParserTest.java b/test/langtools/tools/javac/parser/JavacParserTest.java
index 0b5f67e089f..a22e15bc1f2 100644
--- a/test/langtools/tools/javac/parser/JavacParserTest.java
+++ b/test/langtools/tools/javac/parser/JavacParserTest.java
@@ -23,7 +23,7 @@
 
 /*
  * @test
- * @bug 7073631 7159445 7156633 8028235 8065753 8205418 8205913 8228451 8237041 8253584 8246774 8256411 8256149 8259050 8266436 8267221 8271928 8275097 8293897 8295401 8304671
+ * @bug 7073631 7159445 7156633 8028235 8065753 8205418 8205913 8228451 8237041 8253584 8246774 8256411 8256149 8259050 8266436 8267221 8271928 8275097 8293897 8295401 8304671 8310326
  * @summary tests error and diagnostics positions
  * @author  Jan Lahoda
  * @modules jdk.compiler/com.sun.tools.javac.api
@@ -2395,6 +2395,31 @@ public class JavacParserTest extends TestCase {
                 codes);
     }
 
+    @Test //JDK-8310326
+    void testUnnamedClassPositions() throws IOException {
+        String code = """
+                      void main() {
+                      }
+                      """;
+        DiagnosticCollector<JavaFileObject> coll =
+                new DiagnosticCollector<>();
+        JavacTaskImpl ct = (JavacTaskImpl) tool.getTask(null, fm, coll, List.of("--enable-preview", "--source", System.getProperty("java.specification.version")),
+                null, Arrays.asList(new MyFileObject(code)));
+        Trees trees = Trees.instance(ct);
+        SourcePositions sp = trees.getSourcePositions();
+        CompilationUnitTree cut = ct.parse().iterator().next();
+        new TreeScanner<Void, Void>() {
+            @Override
+            public Void visitClass(ClassTree node, Void p) {
+                assertEquals("Wrong start position", 0, sp.getStartPosition(cut, node));
+                assertEquals("Wrong end position", -1, sp.getEndPosition(cut, node));
+                assertEquals("Wrong modifiers start position", -1, sp.getStartPosition(cut, node.getModifiers()));
+                assertEquals("Wrong modifiers end position", -1, sp.getEndPosition(cut, node.getModifiers()));
+                return super.visitClass(node, p);
+            }
+        }.scan(cut, null);
+    }
+
     void run(String[] args) throws Exception {
         int passed = 0, failed = 0;
         final Pattern p = (args != null && args.length > 0)