diff --git a/bonfire/namespaces.py b/bonfire/namespaces.py
index 4c5948a9..99be26c6 100644
--- a/bonfire/namespaces.py
+++ b/bonfire/namespaces.py
@@ -14,7 +14,7 @@
     whoami,
 )
 from bonfire.processor import process_reservation
-from bonfire.utils import FatalError
+from bonfire.utils import FatalError, hms_to_seconds
 
 
 log = logging.getLogger(__name__)
@@ -279,10 +279,14 @@ def extend_namespace(namespace, duration):
                 res["status"]["namespace"],
             )
             return None
+
+        prev_duration = hms_to_seconds(res["spec"]["duration"])
+        new_duration = prev_duration + hms_to_seconds(duration)
+
         res_config = process_reservation(
             res["metadata"]["name"],
             res["spec"]["requester"],
-            duration,
+            _pretty_time_delta(new_duration),
         )
 
         log.debug("processed reservation:\n%s", res_config)
diff --git a/bonfire/utils.py b/bonfire/utils.py
index f650e42d..3632b017 100644
--- a/bonfire/utils.py
+++ b/bonfire/utils.py
@@ -501,3 +501,22 @@ def check_pypi():
         log.error("unable to parse version info from pypi")
     else:
         _compare_version(pypi_version)
+
+
+def hms_to_seconds(s):
+    fmt = r"^(\d+h)?(\d+m)?(\d+s)?$"
+
+    l = re.split(fmt, s)
+
+    seconds = 0
+
+    for group in l:
+        if group:  # to ignore 'None' groups when all units aren't present
+            if 'h' in group:
+                seconds += int(group.split('h')[0])*3600
+            elif 'm' in group:
+                seconds += int(group.split('m')[0])*60
+            elif 's' in group:
+                seconds += int(group.split('s')[0])
+
+    return seconds