diff --git a/tealish/build.py b/tealish/build.py
index a28d429..f5e4c27 100644
--- a/tealish/build.py
+++ b/tealish/build.py
@@ -17,8 +17,10 @@ def assemble_with_goal(teal: str) -> Tuple[bytes, SourceMap]:
         raise Exception("goal not found in path")
     except subprocess.CalledProcessError as e:
         raise Exception(e.output)
-    bytecode = open(tmp_out_filename, "rb").read()
-    algod_sourcemap = json.load(open(tmp_out_filename + ".map"))
+    with open(tmp_out_filename, "rb") as f:
+        bytecode = f.read()
+    with open(tmp_out_filename + ".map", "r") as f:
+        algod_sourcemap = json.load(f)
     return bytecode, SourceMap(algod_sourcemap)
 
 
diff --git a/tealish/cli.py b/tealish/cli.py
index e5b9668..0ddb010 100644
--- a/tealish/cli.py
+++ b/tealish/cli.py
@@ -36,7 +36,8 @@ def _build(
         teal_filename = output_path / f"{base_filename}.teal"
         if not quiet:
             click.echo(f"Compiling {path} to {teal_filename}")
-        teal, tealish_map = _compile_program(open(path).read())
+        with open(path, "r") as f:
+            teal, tealish_map = _compile_program(f.read())
         teal_string = "\n".join(teal + [""])
         with open(teal_filename, "w") as f:
             f.write("\n".join(teal + [""]))
diff --git a/tealish/langspec.py b/tealish/langspec.py
index fd15047..ce2b5ae 100644
--- a/tealish/langspec.py
+++ b/tealish/langspec.py
@@ -245,7 +245,8 @@ def get_field_type(self, namespace: str, name: str) -> str:
 
 local_lang_spec: Optional[LangSpec] = None
 if os.path.exists("langspec.json"):
-    local_lang_spec = LangSpec(json.load(open("langspec.json")))
+    with open("langspec.json", "r") as f:
+        local_lang_spec = LangSpec(json.load(f))
 
 
 def get_active_langspec() -> LangSpec: