diff --git a/src/hotspot/share/opto/parse2.cpp b/src/hotspot/share/opto/parse2.cpp
index 8ac4cf47558..9cb20cfcd00 100644
--- a/src/hotspot/share/opto/parse2.cpp
+++ b/src/hotspot/share/opto/parse2.cpp
@@ -1749,6 +1749,10 @@ static bool match_type_check(PhaseGVN& gvn,
                              Node* con, const Type* tcon,
                              Node* val, const Type* tval,
                              Node** obj, const TypeOopPtr** cast_type) { // out-parameters
+  assert(tcon->singleton(), "not a constant: %s", Type::str(tcon));
+  assert(tcon == gvn.type(con), "mismatch: %s != %s", Type::str(tcon), Type::str(gvn.type(con)));
+  assert(tval == gvn.type(val), "mismatch: %s != %s", Type::str(tval), Type::str(gvn.type(val)));
+
   // Look for opportunities to sharpen the type of a node whose klass is compared with a constant klass.
   // The constant klass being tested against can come from many bytecode instructions (implicitly or explicitly),
   // and also from profile data used by speculative casts.
@@ -1783,14 +1787,14 @@ static bool match_type_check(PhaseGVN& gvn,
   //              Region
   //                 \  ConI ConI
   //                  \  |  /
-  //          val ->    Phi  ConI  <- con
-  //                     \  /
-  //                     CmpI
-  //                      |
-  //                    Bool [btest]
-  //                      |
+  //            val ->  Phi   ConI|CastII <- con
+  //                      \     /
+  //                       CmpI
+  //                        |
+  //                      Bool [btest]
+  //                        |
   //
-  if (tval->isa_int() && val->is_Phi() && val->in(0)->as_Region()->is_diamond()) {
+  if (tcon->isa_int() && val->is_Phi() && val->in(0)->as_Region()->is_diamond()) {
     RegionNode* diamond = val->in(0)->as_Region();
     IfNode* if1 = diamond->in(1)->in(0)->as_If();
     BoolNode* b1 = if1->in(1)->isa_Bool();
@@ -1799,12 +1803,16 @@ static bool match_type_check(PhaseGVN& gvn,
              b1->_test._test == BoolTest::ne, "%d", b1->_test._test);
 
       ProjNode* success_proj = if1->proj_out(b1->_test._test == BoolTest::eq ? 1 : 0);
-      int idx = diamond->find_edge(success_proj);
-      assert(idx == 1 || idx == 2, "");
-      Node* vcon = val->in(idx);
+      int success_idx = diamond->find_edge(success_proj);
+      assert(success_idx == 1 || success_idx == 2, "");
+      assert(val->req() == 3, "not a diamond");
 
-      if ((btest == BoolTest::eq && vcon == con) || (btest == BoolTest::ne && vcon != con)) {
-        assert(val->find_edge(con) > 0, "mismatch");
+      // gen_instanceof() emits 1 on success and 0 on failure.
+      // Check whether current comparison selects the success value.
+      const Type* success_tval = gvn.type(val->in(success_idx));
+      assert(success_tval->isa_int(), "not an int: %s", Type::str(success_tval));
+      if ((btest == BoolTest::eq && tcon == success_tval) ||
+          (btest == BoolTest::ne && tcon->join(success_tval)->empty())) {
         SubTypeCheckNode* sub = b1->in(1)->as_SubTypeCheck();
         Node* obj_or_subklass = sub->in(SubTypeCheckNode::ObjOrSubKlass);
         Node* superklass = sub->in(SubTypeCheckNode::SuperKlass);
diff --git a/test/hotspot/jtreg/compiler/types/TestSubTypeCheckConstantCastII.java b/test/hotspot/jtreg/compiler/types/TestSubTypeCheckConstantCastII.java
new file mode 100644
index 00000000000..d3ce317ed30
--- /dev/null
+++ b/test/hotspot/jtreg/compiler/types/TestSubTypeCheckConstantCastII.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8382536
+ * @summary C2: sharpen_type_after_if: assert(val->find_edge(con) > 0) failed: mismatch
+ *
+ * @run main/othervm -Xcomp -XX:CompileCommand=compileonly,${test.main.class}::test ${test.main.class}
+ */
+package compiler.types;
+
+public class TestSubTypeCheckConstantCastII {
+    static class A {}
+
+    static boolean isInstanceOfA(Object obj) {
+        return (obj instanceof A);
+    }
+
+    static void test(boolean b, Object obj) {
+        if (b) {
+            return;
+        }
+        // b == false
+        if (b != isInstanceOfA(obj)) {}
+    }
+
+    public static void main(String[] args) {
+        test(true, new A());
+    }
+}