diff --git a/gi-gtk-hs.cabal b/gi-gtk-hs.cabal
--- a/gi-gtk-hs.cabal
+++ b/gi-gtk-hs.cabal
@@ -1,5 +1,5 @@
 name:                gi-gtk-hs
-version:             0.3.6.2
+version:             0.3.6.3
 synopsis:            A wrapper for gi-gtk, adding a few more idiomatic API parts on top
 description:         A wrapper for gi-gtk, adding a few more idiomatic API parts on top
 homepage:            https://github.com/haskell-gi/gi-gtk-hs
@@ -31,7 +31,7 @@
                        base-compat >=0.9.0 && <0.11,
                        mtl >=2.1 && <2.3,
                        transformers >=0.3.0.0 && <0.6,
-                       containers >=0.5.5.1 && <0.6,
+                       containers >=0.5.5.1 && <0.7,
                        text >=1.2 && <1.3,
                        haskell-gi-base >=0.21.2 && <0.22,
                        gi-glib >=2.0.6 && <2.1,
diff --git a/src/Data/GI/Gtk/ComboBox.hs b/src/Data/GI/Gtk/ComboBox.hs
--- a/src/Data/GI/Gtk/ComboBox.hs
+++ b/src/Data/GI/Gtk/ComboBox.hs
@@ -186,8 +186,10 @@
 --
 comboBoxGetModelText :: (MonadIO m, IsComboBox self) => self -> m (SeqStore Text)
 comboBoxGetModelText self = do
-  (Just store) <- objectGetAttributeUnsafe self comboQuark
-  return store
+  maybeStore <- objectGetAttributeUnsafe self comboQuark
+  case maybeStore of
+    Just store -> return store
+    Nothing -> error "Could not get required attribute"
 
 -- | Appends @string@ to the list of strings stored in @comboBox@. Note that
 -- you can only use this function with combo boxes constructed with