diff --git a/spacy/pipeline.pyx b/spacy/pipeline.pyx
index a2321d1ad..e5f426453 100644
--- a/spacy/pipeline.pyx
+++ b/spacy/pipeline.pyx
@@ -441,11 +441,12 @@ class Tagger(Pipe):
     def add_label(self, label):
         if label in self.labels:
             return 0
-        smaller = self.model[-1]._layers[-1]
-        larger = Softmax(len(self.labels)+1, smaller.nI)
-        copy_array(larger.W[:smaller.nO], smaller.W)
-        copy_array(larger.b[:smaller.nO], smaller.b)
-        self.model[-1]._layers[-1] = larger
+        if self.model not in (True, False, None):
+            smaller = self.model._layers[-1]
+            larger = Softmax(len(self.labels)+1, smaller.nI)
+            copy_array(larger.W[:smaller.nO], smaller.W)
+            copy_array(larger.b[:smaller.nO], smaller.b)
+            self.model._layers[-1] = larger
         self.labels.append(label)
         return 1
 
@@ -759,11 +760,12 @@ class TextCategorizer(Pipe):
     def add_label(self, label):
         if label in self.labels:
             return 0
-        smaller = self.model[-1]._layers[-1]
-        larger = Affine(len(self.labels)+1, smaller.nI)
-        copy_array(larger.W[:smaller.nO], smaller.W)
-        copy_array(larger.b[:smaller.nO], smaller.b)
-        self.model[-1]._layers[-1] = larger
+        if self.model not in (None, True, False):
+            smaller = self.model._layers[-1]
+            larger = Affine(len(self.labels)+1, smaller.nI)
+            copy_array(larger.W[:smaller.nO], smaller.W)
+            copy_array(larger.b[:smaller.nO], smaller.b)
+            self.model._layers[-1] = larger
         self.labels.append(label)
         return 1