diff --git a/base-test/org.eclipse.jdt.groovy.core.tests.compiler/src/org/eclipse/jdt/groovy/core/tests/xform/StaticCompilationTests.java b/base-test/org.eclipse.jdt.groovy.core.tests.compiler/src/org/eclipse/jdt/groovy/core/tests/xform/StaticCompilationTests.java
index 83760bca28..8935a9a15f 100644
--- a/base-test/org.eclipse.jdt.groovy.core.tests.compiler/src/org/eclipse/jdt/groovy/core/tests/xform/StaticCompilationTests.java
+++ b/base-test/org.eclipse.jdt.groovy.core.tests.compiler/src/org/eclipse/jdt/groovy/core/tests/xform/StaticCompilationTests.java
@@ -807,16 +807,41 @@ public void testCompileStatic6137() {
         String[] sources = {
             "Main.groovy",
             "@groovy.transform.CompileStatic\n" +
-            "void test(a, b) {\n" +
-            "  print(a in b)\n" +
+            "void test() {\n" +
+            "  print(null in null)\n" +
+            "  print(null in 'xx')\n" +
+            "  print('xx' in null)\n" +
+            "  print('xx' in 'xx')\n" +
+            "  print('xx' in ['xx'])\n" +
             "}\n" +
-            "test(null,null)\n" +
-            "test(null,new Object())\n" +
-            "test(new Object(),null)\n",
+            "test()\n",
         };
         //@formatter:on
 
-        runConformTest(sources, "truefalsefalse");
+        runConformTest(sources, "truefalsefalsetruetrue");
+    }
+
+    @Test
+    public void testCompileStatic6137a() {
+        assumeTrue(isParrotParser());
+
+        //@formatter:off
+        String[] sources = {
+            "Main.groovy",
+            "@groovy.transform.CompileStatic\n" +
+            "void test() {\n" +
+            "  print(null !in null)\n" +
+            "  print(null !in 'xx')\n" +
+            "  print('xx' !in null)\n" +
+            "  print('xx' !in 'xx')\n" +
+            "  print('xx' !in [''])\n" +
+            "  print('xx' !in ['xx'])\n" +
+            "}\n" +
+            "test()\n",
+        };
+        //@formatter:on
+
+        runConformTest(sources, "falsetruetruefalsetruefalse");
     }
 
     @Test
@@ -1347,7 +1372,10 @@ public void testCompileStatic7473a() {
         runConformTest(sources, "not xyz");
 
         String result = disassemble(getOutputFile("Main.class"), 1);
-        int pos = result.indexOf("createList");
+        int pos = result.indexOf("ScriptBytecodeAdapter.isNotCase");
+        if (isAtLeastGroovy(40)) assertTrue(pos < 0); //GROOVY-10383
+
+        pos = result.indexOf("createList");
         assumeTrue(pos > 0);
 
         // the operand should be processed only once
diff --git a/base/org.codehaus.groovy40/src/org/codehaus/groovy/transform/sc/transformers/BinaryExpressionTransformer.java b/base/org.codehaus.groovy40/src/org/codehaus/groovy/transform/sc/transformers/BinaryExpressionTransformer.java
index c2f728dd33..4a06c775d2 100644
--- a/base/org.codehaus.groovy40/src/org/codehaus/groovy/transform/sc/transformers/BinaryExpressionTransformer.java
+++ b/base/org.codehaus.groovy40/src/org/codehaus/groovy/transform/sc/transformers/BinaryExpressionTransformer.java
@@ -62,7 +62,6 @@
 import static org.codehaus.groovy.ast.tools.GeneralUtils.callX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.classX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.constX;
-import static org.codehaus.groovy.ast.tools.GeneralUtils.isNullX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.isOrImplements;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.ternaryX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.varX;
@@ -116,7 +115,9 @@ public Expression transformBinaryExpression(final BinaryExpression bin) {
             }
             break;
           case Types.KEYWORD_IN:
-            return transformInOperation(bin);
+            equal = true; //fallthrough
+          case Types.COMPARE_NOT_IN:
+            return transformInOperation(bin, equal);
           case Types.COMPARE_EQUAL:
           case Types.COMPARE_IDENTICAL:
             equal = true; //fallthrough
@@ -227,12 +228,12 @@ private static Expression transformAssignmentToSetterCall(
                 pos);
     }
 
-    private Expression transformInOperation(final BinaryExpression bin) {
+    private Expression transformInOperation(final BinaryExpression bin, final boolean in) {
         Expression leftExpression = bin.getLeftExpression();
         Expression rightExpression = bin.getRightExpression();
 
-        // transform "left in right" into "right.isCase(left)"
-        MethodCallExpression call = callX(rightExpression, "isCase", leftExpression);
+        // transform "left [!]in right" into "right.is[Not]Case(left)"
+        MethodCallExpression call = callX(rightExpression, in ? "isCase" : "isNotCase", leftExpression);
         call.setImplicitThis(false); call.setSourcePosition(bin); call.copyNodeMetaData(bin);
         call.setMethodTarget(bin.getNodeMetaData(StaticTypesMarker.DIRECT_METHOD_CALL_TARGET));
         // GROOVY-7473: no null test for simple cases
@@ -246,7 +247,7 @@ private Expression transformInOperation(final BinaryExpression bin) {
 
         // GROOVY-6137, GROOVY-7473: null safety and one-time evaluation
         call.setObjectExpression(rightExpression = transformRepeatedReference(rightExpression));
-        Expression safe = ternaryX(isNullX( rightExpression ), isNullX( leftExpression ), call);
+        Expression safe = ternaryX(new CompareToNullExpression(rightExpression,true), new CompareToNullExpression(leftExpression,in), call);
         safe.putNodeMetaData("classgen.callback", classgenCallback(call.getObjectExpression()));
         return staticCompilationTransformer.transform(safe);
     }