diff --git a/src/main/java/forge/ImageCache.java b/src/main/java/forge/ImageCache.java
index a4b7b5435b6..b73cbef1ef4 100644
--- a/src/main/java/forge/ImageCache.java
+++ b/src/main/java/forge/ImageCache.java
@@ -197,6 +197,7 @@ public class ImageCache {
      * Returns the Image corresponding to the key.
      */
     private static BufferedImage getImage(final String key) {
+        FThreads.assertExecutedByEdt(true);
         try {
             return ImageCache._CACHE.get(key);
         } catch (final ExecutionException ex) {