diff --git a/android/src/main/java/com/sbugert/rnadmob/RNAdMobInterstitialAdModule.java b/android/src/main/java/com/sbugert/rnadmob/RNAdMobInterstitialAdModule.java
index e53032641..79efff12e 100644
--- a/android/src/main/java/com/sbugert/rnadmob/RNAdMobInterstitialAdModule.java
+++ b/android/src/main/java/com/sbugert/rnadmob/RNAdMobInterstitialAdModule.java
@@ -106,7 +106,9 @@ private void sendEvent(String eventName, @Nullable WritableMap params) {
 
     @ReactMethod
     public void setAdUnitID(String adUnitID) {
-        mInterstitialAd.setAdUnitId(adUnitID);
+        if (mInterstitialAd.getAdUnitId() == null) {
+            mInterstitialAd.setAdUnitId(adUnitID);
+        }
     }
 
     @ReactMethod