diff --git a/src/util.cpp b/src/util.cpp
index 8d21ff45..ae948ea0 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -160,7 +160,10 @@ std::string GetExtension(std::string url) {
 }
 
 bool IsURLViewableImage(const std::string &url) {
-    const auto ext = GetExtension(url);
+    std::string lw_url = url;
+    std::transform(lw_url.begin(), lw_url.end(), lw_url.begin(), ::tolower);
+
+    const auto ext = GetExtension(lw_url);
     static const char *exts[] = { ".jpeg",
                                   ".jpg",
                                   ".png", nullptr };