diff --git a/plugins/InspectionGadgets/src/com/siyeh/ig/psiutils/InstanceOfUtils.java b/plugins/InspectionGadgets/src/com/siyeh/ig/psiutils/InstanceOfUtils.java
index 68eaa0c19b66..702d84d522ac 100644
--- a/plugins/InspectionGadgets/src/com/siyeh/ig/psiutils/InstanceOfUtils.java
+++ b/plugins/InspectionGadgets/src/com/siyeh/ig/psiutils/InstanceOfUtils.java
@@ -113,6 +113,9 @@ public class InstanceOfUtils {
       }
       else if (tokenType == JavaTokenType.OROR) {
         for (PsiExpression operand : expression.getOperands()) {
+          if (operand instanceof PsiPrefixExpression && ((PsiPrefixExpression)operand).getOperationTokenType() == JavaTokenType.EXCL) {
+            inElse = true;
+          }
           checkExpression(operand);
         }
         if (inElse && conflictingInstanceof != null) {
@@ -125,8 +128,7 @@ public class InstanceOfUtils {
     public void visitIfStatement(PsiIfStatement ifStatement) {
       final PsiStatement branch = ifStatement.getElseBranch();
       inElse = branch != null &&
-               PsiTreeUtil.isAncestor(branch, referenceExpression,
-                                      true);
+               PsiTreeUtil.isAncestor(branch, referenceExpression, true);
       if (inElse) {
         if (branch instanceof PsiBlockStatement) {
           final PsiBlockStatement blockStatement =
@@ -161,8 +163,7 @@ public class InstanceOfUtils {
     }
 
     @Override
-    public void visitConditionalExpression(
-      PsiConditionalExpression expression) {
+    public void visitConditionalExpression(PsiConditionalExpression expression) {
       final PsiExpression elseExpression =
         expression.getElseExpression();
       inElse = elseExpression != null &&
diff --git a/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/castConflictingInstanceof/notOr/NotOr.java b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/castConflictingInstanceof/notOr/NotOr.java
new file mode 100644
index 000000000000..15c0199b3b0d
--- /dev/null
+++ b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/castConflictingInstanceof/notOr/NotOr.java
@@ -0,0 +1,11 @@
+interface I1 {}
+interface I2 extends I1{}
+interface I3 extends I1 {}
+
+class PP {
+    void f(Object o) {
+        if (o instanceof I1) {
+            if (!(o instanceof I2) || ((I2)o).getClass() != null){}
+        }
+    }
+}
\ No newline at end of file
diff --git a/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/castConflictingInstanceof/notOr/expected.xml b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/castConflictingInstanceof/notOr/expected.xml
new file mode 100644
index 000000000000..580a889dbfd6
--- /dev/null
+++ b/plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/castConflictingInstanceof/notOr/expected.xml
@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems>
+</problems>
diff --git a/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/CastConflictsWithInstanceofInspectionTest.java b/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/CastConflictsWithInstanceofInspectionTest.java
index e7593bfa5d39..ff6d488a6fd9 100644
--- a/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/CastConflictsWithInstanceofInspectionTest.java
+++ b/plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/CastConflictsWithInstanceofInspectionTest.java
@@ -38,6 +38,10 @@ public class CastConflictsWithInstanceofInspectionTest extends IGInspectionTestC
   public void testPolyadic() throws Exception {
     doTest();
   }
+  
+  public void testNotOr() throws Exception {
+    doTest();
+  }
 
   private void doTest() throws Exception {
     doTest("com/siyeh/igtest/bugs/castConflictingInstanceof/" + getTestName(true), new CastConflictsWithInstanceofInspection());