diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 9a5db747f..ef87c1ff8 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -40,7 +40,7 @@ jobs:
           python -m pip install dist/*.whl
 
       - name: Run tests
-        run: "python -m pytest -s -v --cov=httpstan tests"
+        run: python -m pytest -s -v --cov=httpstan tests
 
       - name: Test PyStan compatibility
         run: |
diff --git a/httpstan/models.py b/httpstan/models.py
index 1f937e9b0..f0206b040 100644
--- a/httpstan/models.py
+++ b/httpstan/models.py
@@ -151,7 +151,7 @@ async def build_services_extension_module(program_code: str, extra_compile_args:
     # where to find shared libraries during execution. There are two ways for an
     # extension module to find shared libraries: LD_LIBRARY_PATH and rpath.
     libraries = ["sundials_cvodes", "sundials_idas", "sundials_nvecserial", "tbb"]
-    if platform.system() == "Darwin":
+    if platform.system() == "Darwin":  # pragma: no cover
         libraries.extend(["tbbmalloc", "tbbmalloc_proxy"])
     extension = setuptools.Extension(
         f"stan_services_{stan_model_name}",  # filename only. Module name is "stan_services"
diff --git a/httpstan/schemas.py b/httpstan/schemas.py
index e9f774ad2..80359268c 100644
--- a/httpstan/schemas.py
+++ b/httpstan/schemas.py
@@ -23,9 +23,9 @@ class Operation(marshmallow.Schema):
     @marshmallow.validates_schema
     def validate_result(self, data: dict, many: bool, partial: bool) -> None:
         assert not many and not partial, "Use of `many` and `partial` with schema unsupported."
-        if data["done"] and data.get("result") is None:
+        if data["done"] and data.get("result") is None:  # pragma: no cover
             raise marshmallow.ValidationError("If `done` then `result` must be set.", "result")
-        if not data["done"] and data.get("result"):
+        if not data["done"] and data.get("result"):  # pragma: no cover
             raise marshmallow.ValidationError("If not `done` then `result` must be empty.", "result")
 
 
diff --git a/httpstan/views.py b/httpstan/views.py
index e69e3e20c..d2fae0359 100644
--- a/httpstan/views.py
+++ b/httpstan/views.py
@@ -112,7 +112,7 @@ async def handle_create_model(request: aiohttp.web.Request) -> aiohttp.web.Respo
     try:
         # `build_services_extension_module` has side-effect of storing extension module in cache
         compiler_output = await httpstan.models.build_services_extension_module(program_code)
-    except Exception as exc:
+    except Exception as exc:  # pragma: no cover
         message, status = (
             f"Exception while building model extension module: `{repr(exc)}`, traceback: `{traceback.format_tb(exc.__traceback__)}`",
             400,
diff --git a/pyproject.toml b/pyproject.toml
index aff795629..a4f6260ec 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -67,7 +67,7 @@ known_local_folder = "helpers"
 
 [tool.coverage.run]
 branch = true
-omit = httpstan/__main__.py
+omit = ["httpstan/__main__.py"]
 
 [tool.coverage.report]
 fail_under = 95