diff --git a/qutebrowser/models/completion.py b/qutebrowser/models/completion.py
index ef002ddbb..16e72372d 100644
--- a/qutebrowser/models/completion.py
+++ b/qutebrowser/models/completion.py
@@ -17,6 +17,7 @@
 
 """The base completion model for completion in the command line."""
 
+import logging
 from PyQt5.QtCore import Qt, QVariant, QAbstractItemModel, QModelIndex
 
 
@@ -160,11 +161,7 @@ class CompletionModel(QAbstractItemModel):
         if not parent.isValid():
             pitem = self._root
         else:
-            try:
-                pitem = self._id_map[parent.internalId()]
-            except KeyError:
-                from qutebrowser.utils.debug import set_trace; set_trace()
-
+            pitem = self._id_map[parent.internalId()]
         return len(pitem.children)
 
     def data(self, index, role=Qt.DisplayRole):
@@ -273,6 +270,9 @@ class CompletionModel(QAbstractItemModel):
             A generated QModelIndex or an invalid QModelIndex on failure.
 
         """
+        if parent.model() is not None and parent.model() is not self:
+            logging.debug("row {}, column {}, parent {}, parentmodel {}, self {}".format(row, column, parent, parent.model(), self))
+            from qutebrowser.utils.debug import set_trace; set_trace()
         if (0 <= row < self.rowCount(parent) and
                 0 <= column < self.columnCount(parent)):
             pass
diff --git a/qutebrowser/models/completionfilter.py b/qutebrowser/models/completionfilter.py
index f4493671c..55e5815e6 100644
--- a/qutebrowser/models/completionfilter.py
+++ b/qutebrowser/models/completionfilter.py
@@ -22,6 +22,8 @@ Contains:
 
 """
 
+import logging
+
 from PyQt5.QtCore import QSortFilterProxyModel, QModelIndex
 
 
@@ -31,13 +33,11 @@ class CompletionFilterModel(QSortFilterProxyModel):
 
     Attributes:
         _pattern: The pattern to filter with, used in pattern property.
-        _srcmodel: The source model, accessed via the srcmodel property.
 
     """
 
     def __init__(self, parent=None):
         super().__init__(parent)
-        self._srcmodel = None
         self._pattern = ''
 
     @property
@@ -61,31 +61,13 @@ class CompletionFilterModel(QSortFilterProxyModel):
         self._pattern = val
         self.invalidateFilter()
         sortcol = 0
-        if self.srcmodel is not None:
+        if self.sourceModel() is not None:
             try:
-                self.srcmodel.sort(sortcol)
+                self.sourceModel().sort(sortcol)
             except NotImplementedError:
                 self.sort(sortcol)
             self.invalidate()
 
-    @property
-    def srcmodel(self):
-        """Getter for srcmodel."""
-        return self._srcmodel
-
-    @srcmodel.setter
-    def srcmodel(self, model):
-        """Set a new source model and clear the pattern.
-
-        Args:
-            model: The new source model.
-
-        """
-        # FIXME change this to a property
-        self.setSourceModel(model)
-        self._srcmodel = model
-        self.pattern = ''
-
     def first_item(self):
         """Return the first item in the model."""
         cat = self.index(0, 0)
@@ -96,6 +78,11 @@ class CompletionFilterModel(QSortFilterProxyModel):
         cat = self.index(self.rowCount() - 1, 0)
         return self.index(self.rowCount(cat) - 1, 0, cat)
 
+    def setSourceModel(self, model):
+        logging.debug("Setting source model: {}".format(model))
+        self.pattern = ''
+        super().setSourceModel(model)
+
     def filterAcceptsRow(self, row, parent):
         """Custom filter implementation.
 
@@ -112,8 +99,8 @@ class CompletionFilterModel(QSortFilterProxyModel):
         """
         if parent == QModelIndex():
             return True
-        idx = self.srcmodel.index(row, 0, parent)
-        data = self.srcmodel.data(idx).value()
+        idx = self.sourceModel().index(row, 0, parent)
+        data = self.sourceModel().data(idx).value()
         # TODO more sophisticated filtering
         if not self.pattern:
             return True
@@ -133,8 +120,8 @@ class CompletionFilterModel(QSortFilterProxyModel):
             True if left < right, else False
 
         """
-        left = self.srcmodel.data(lindex).value()
-        right = self.srcmodel.data(rindex).value()
+        left = self.sourceModel().data(lindex).value()
+        right = self.sourceModel().data(rindex).value()
 
         leftstart = left.startswith(self.pattern)
         rightstart = right.startswith(self.pattern)
diff --git a/qutebrowser/widgets/completion.py b/qutebrowser/widgets/completion.py
index ae679064c..3ac35487e 100644
--- a/qutebrowser/widgets/completion.py
+++ b/qutebrowser/widgets/completion.py
@@ -160,7 +160,7 @@ class CompletionView(QTreeView):
             model: A QAbstractItemModel with available completions.
 
         """
-        self.model.srcmodel = self._completion_models[model]
+        self.model.setSourceModel(self._completion_models[model])
         self.expandAll()
         self.resizeColumnToContents(0)
 
@@ -201,7 +201,7 @@ class CompletionView(QTreeView):
         if text:
             text = text.split()[-1]
         self.model.pattern = text
-        self.model.srcmodel.mark_all_items(text)
+        self.model.sourceModel().mark_all_items(text)
         if self._enabled:
             self.show()
 
diff --git a/qutebrowser/widgets/crash.py b/qutebrowser/widgets/crash.py
index 18d2afb86..6d951adcc 100644
--- a/qutebrowser/widgets/crash.py
+++ b/qutebrowser/widgets/crash.py
@@ -111,7 +111,8 @@ class CrashDialog(QDialog):
         ]
         chunks = []
         for (header, body) in outputs:
-            h = '==== {} ===='.format(header)
-            chunks.append('\n'.join([h, body]))
+            if body is not None:
+                h = '==== {} ===='.format(header)
+                chunks.append('\n'.join([h, body]))
 
         return '\n\n'.join(chunks)