diff --git a/cwl_utils/image_puller.py b/cwl_utils/image_puller.py
index beec3c31..5fae0781 100644
--- a/cwl_utils/image_puller.py
+++ b/cwl_utils/image_puller.py
@@ -89,7 +89,7 @@ def save_docker_image(self) -> None:
 class SingularityImagePuller(ImagePuller):
     """Pull docker image with Singularity."""
 
-    CHARS_TO_REPLACE = ["/"]
+    CHARS_TO_REPLACE = ["/", ":"]
     NEW_CHAR = "_"
 
     def get_image_name(self) -> str: