diff --git a/src/ozzy/part_mixin.py b/src/ozzy/part_mixin.py
index b87dc74..306b31c 100644
--- a/src/ozzy/part_mixin.py
+++ b/src/ozzy/part_mixin.py
@@ -37,7 +37,7 @@ def _define_q_units(raw_sdims, rvar_attrs: dict | None):
             for ustr in ustrings:
                 extra += rf"/ {ustr}"
             if rvar_attrs is not None:
-                extra += rf"/ {rvar_attrs["units"].strip("$")}"
+                extra += rf"/ {rvar_attrs['units'].strip('$')}"
             units_str = rf"$Q_w {extra}$"
         else:
             units_str = "a.u."