diff --git a/lib/galaxy/tool_util/deps/requirements.py b/lib/galaxy/tool_util/deps/requirements.py
index 53fdb51d1657..d2fbb249aa63 100644
--- a/lib/galaxy/tool_util/deps/requirements.py
+++ b/lib/galaxy/tool_util/deps/requirements.py
@@ -189,11 +189,17 @@ def __init__(
     ) -> None:
         # Force to lowercase because container image names must be lowercase.
         # Cached singularity images include the path on disk, so only lowercase
-        # the image identifier portion.
+        # the image identifier portion. Note, the tag can also contain upper case
+        # letters.
         self.identifier = identifier
         if identifier:
             parts = identifier.rsplit(os.sep, 1)
-            parts[-1] = parts[-1].lower()
+            if ":" in parts[-1]:
+                name, tag = parts[-1].rsplit(":", 1)
+                parts[-1] = f"{name.lower()}:{tag}"
+            else:
+                parts[-1] = parts[-1].lower()
+
             self.identifier = os.sep.join(parts)
         self.type = type
         self.resolve_dependencies = resolve_dependencies