Index: /trunk/src/org/openstreetmap/josm/data/cache/JCSCachedTileLoaderJob.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/cache/JCSCachedTileLoaderJob.java	(revision 17504)
+++ /trunk/src/org/openstreetmap/josm/data/cache/JCSCachedTileLoaderJob.java	(revision 17505)
@@ -7,4 +7,5 @@
 import java.net.URL;
 import java.security.SecureRandom;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -187,8 +188,10 @@
      * Simple implementation. All errors should be cached as empty. Though some JDK (JDK8 on Windows for example)
      * doesn't return 4xx error codes, instead they do throw an FileNotFoundException or IOException
+     * @param responseCode
+     * @param headerFields
      *
      * @return true if we should put empty object into cache, regardless of what remote resource has returned
      */
-    protected boolean cacheAsEmpty() {
+    protected boolean cacheAsEmpty(Map<String, List<String>> headerFields, int responseCode) {
         return attributes.getResponseCode() < 500;
     }
@@ -371,5 +374,5 @@
                             getCacheKey(), raw.length, getUrl());
                     return true;
-                } else if (cacheAsEmpty()) {
+                } else if (cacheAsEmpty(urlConn.getHeaderFields(), urlConn.getResponseCode())) {
                     cacheData = createCacheEntry(new byte[]{});
                     cache.put(getCacheKey(), cacheData, attributes);
@@ -386,5 +389,5 @@
             attributes.setError(e);
             attributes.setException(e);
-            boolean doCache = isResponseLoadable(null, 404, null) || cacheAsEmpty();
+            boolean doCache = isResponseLoadable(null, 404, null) || cacheAsEmpty(Collections.emptyMap(), 404);
             if (doCache) {
                 cacheData = createCacheEntry(new byte[]{});
Index: /trunk/src/org/openstreetmap/josm/data/imagery/TMSCachedTileLoaderJob.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/imagery/TMSCachedTileLoaderJob.java	(revision 17504)
+++ /trunk/src/org/openstreetmap/josm/data/imagery/TMSCachedTileLoaderJob.java	(revision 17505)
@@ -135,10 +135,32 @@
             return false; // do no try to load data from no-tile at zoom, cache empty object instead
         }
+        if (isNotImage(headers, statusCode)) {
+            String message = detectErrorMessage( new String(content, StandardCharsets.UTF_8));
+            if (message != null && !message.isEmpty()) {
+                tile.setError(message);
+            }
+            return false;
+        }
         return super.isResponseLoadable(headers, statusCode, content);
     }
 
-    @Override
-    protected boolean cacheAsEmpty() {
-        return isNoTileAtZoom() || super.cacheAsEmpty();
+    private boolean isNotImage(Map<String, List<String>> headers, int statusCode) {
+        if (statusCode == 200 && headers.containsKey("Content-Type") && !headers.get("Content-Type").isEmpty()) {
+            String contentType = headers.get("Content-Type").stream().findAny().get();
+            if (contentType !=null && !contentType.startsWith("image")) {
+                Logging.warn("Image not returned for tile: " + url + " content type was: " + contentType);
+                // not an image - do not store response in cache, so next time it will be queried again from the server
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    protected boolean cacheAsEmpty(Map<String, List<String>> headerFields, int responseCode) {
+        if (isNotImage(headerFields, responseCode)) {
+            return false;
+        }
+        return isNoTileAtZoom() || super.cacheAsEmpty(headerFields, responseCode);
     }
 
@@ -211,4 +233,8 @@
 
     private void handleError(CacheEntryAttributes attributes) {
+        if (tile.hasError() && tile.getErrorMessage() != null) {
+            // tile has already set error message, don't overwrite it
+            return;
+        }
         if (attributes != null) {
             int httpStatusCode = attributes.getResponseCode();