diff --git a/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBFactory.java b/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBFactory.java
index d02056fbc..4af07a6c3 100644
--- a/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBFactory.java
+++ b/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBFactory.java
@@ -28,7 +28,7 @@ public abstract class IDBFactory implements JSObject {
 
     public static IDBFactory getInstance() {
         IDBFactory factory = getInstanceImpl();
-        if (!factory.isUndefined()) {
+        if (factory.isUndefined()) {
             throw new IllegalStateException("IndexedDB is not supported in this browser");
         }
         return factory;
diff --git a/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBObjectStore.java b/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBObjectStore.java
index 167189b34..a955680b9 100644
--- a/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBObjectStore.java
+++ b/jso/apis/src/main/java/org/teavm/jso/indexeddb/IDBObjectStore.java
@@ -36,8 +36,8 @@ public abstract class IDBObjectStore implements JSObject, IDBCursorSource {
         }
     }
 
-    @JSBody(script = "return this;")
-    private native String[] unwrapStringArray(JSObject obj);
+    @JSBody(params = "obj", script = "return obj;")
+    private static native String[] unwrapStringArray(JSObject obj);
 
     @JSProperty
     public abstract String[] getIndexNames();