diff --git a/gptc/compiler.py b/gptc/compiler.py
index 3372e70..b54b85e 100755
--- a/gptc/compiler.py
+++ b/gptc/compiler.py
@@ -1,9 +1,12 @@
 # SPDX-License-Identifier: LGPL-3.0-or-later
 
 import gptc.tokenizer
+from typing import Iterable, Mapping, List, Dict, Union
 
 
-def compile(raw_model, max_ngram_length=1):
+def compile(
+    raw_model: Iterable[Mapping[str, str]], max_ngram_length: int = 1
+) -> Dict[str, Union[int, List[Union[str, int]]]]:
     """Compile a raw model.
 
     Parameters
@@ -21,7 +24,7 @@ def compile(raw_model, max_ngram_length=1):
 
     """
 
-    categories = {}
+    categories: Dict[str, str] = {}
 
     for portion in raw_model:
         text = gptc.tokenizer.tokenize(portion["text"], max_ngram_length)
@@ -31,7 +34,7 @@ def compile(raw_model, max_ngram_length=1):
         except KeyError:
             categories[category] = text
 
-    categories_by_count = {}
+    categories_by_count: Dict[str, Dict[str, float]] = {}
 
     names = []
 
@@ -49,7 +52,7 @@ def compile(raw_model, max_ngram_length=1):
                 categories_by_count[category][word] = 1 / len(
                     categories[category]
                 )
-    word_weights = {}
+    word_weights: Dict[str, Dict[str, float]] = {}
     for category, words in categories_by_count.items():
         for word, value in words.items():
             try:
@@ -57,7 +60,7 @@ def compile(raw_model, max_ngram_length=1):
             except KeyError:
                 word_weights[word] = {category: value}
 
-    model = {}
+    model: Dict[str, Union[int, List[Union[str, int]]]] = {}
     for word, weights in word_weights.items():
         total = sum(weights.values())
         model[word] = []