diff --git a/core/src/main/java/org/teavm/model/emit/ValueEmitter.java b/core/src/main/java/org/teavm/model/emit/ValueEmitter.java
index 4a86fe311..a4e16c315 100644
--- a/core/src/main/java/org/teavm/model/emit/ValueEmitter.java
+++ b/core/src/main/java/org/teavm/model/emit/ValueEmitter.java
@@ -748,6 +748,9 @@ public class ValueEmitter {
         if (!pe.hierarchy.isSuperType(targetClass, boxClassName, false)) {
             throw new EmitException("Can't convert " + this.type + " to " + targetClass);
         }
+        if (!result.type.equals(type)) {
+            result.type = type;
+        }
         return result;
     }
 
diff --git a/tests/src/test/java/org/teavm/vm/LambdaTest.java b/tests/src/test/java/org/teavm/vm/LambdaTest.java
index f8e476f76..8a40cbc10 100644
--- a/tests/src/test/java/org/teavm/vm/LambdaTest.java
+++ b/tests/src/test/java/org/teavm/vm/LambdaTest.java
@@ -18,6 +18,7 @@ package org.teavm.vm;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import java.io.Serializable;
+import java.util.function.IntPredicate;
 import java.util.function.Supplier;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -41,6 +42,23 @@ public class LambdaTest {
         assertTrue("Supplier is expected to implement Serializable", supplier instanceof Serializable);
     }
 
+    @Test
+    public void boxParameterToSupertype() {
+        assertEquals(".*.*.*.*.*", acceptIntPredicate(this::oddPredicate));
+    }
+
+    private String acceptIntPredicate(IntPredicate p) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < 10; ++i) {
+            sb.append(p.test(i) ? '*' : '.');
+        }
+        return sb.toString();
+    }
+
+    private boolean oddPredicate(Object o) {
+        return o instanceof Integer && ((Integer) o) % 2 != 0;
+    }
+
     interface A {
     }
 }