8335b1
diff --git a/modules/cache/cache_util.c b/modules/cache/cache_util.c
8335b1
index 7b7fb45..fbebb1e 100644
8335b1
--- a/modules/cache/cache_util.c
8335b1
+++ b/modules/cache/cache_util.c
8335b1
@@ -1251,8 +1251,10 @@ CACHE_DECLARE(apr_table_t *)ap_cache_cacheable_headers_out(request_rec *r)
8335b1
 
8335b1
     if (!apr_table_get(headers_out, "Content-Type")
8335b1
         && r->content_type) {
8335b1
-        apr_table_setn(headers_out, "Content-Type",
8335b1
-                       ap_make_content_type(r, r->content_type));
8335b1
+        const char *ctype = ap_make_content_type(r, r->content_type);
8335b1
+        if (ctype) {
8335b1
+            apr_table_setn(headers_out, "Content-Type", ctype);
8335b1
+        }
8335b1
     }
8335b1
 
8335b1
     if (!apr_table_get(headers_out, "Content-Encoding")