diff --git a/.github/contributors/tupui.md b/.github/contributors/tupui.md
new file mode 100644
index 000000000..5f53a72f8
--- /dev/null
+++ b/.github/contributors/tupui.md
@@ -0,0 +1,106 @@
+# spaCy contributor agreement
+
+This spaCy Contributor Agreement (**"SCA"**) is based on the
+[Oracle Contributor Agreement](http://www.oracle.com/technetwork/oca-405177.pdf).
+The SCA applies to any contribution that you make to any product or project
+managed by us (the **"project"**), and sets out the intellectual property rights
+you grant to us in the contributed materials. The term **"us"** shall mean
+[ExplosionAI GmbH](https://explosion.ai/legal). The term
+**"you"** shall mean the person or entity identified below.
+
+If you agree to be bound by these terms, fill in the information requested
+below and include the filled-in version with your first pull request, under the
+folder [`.github/contributors/`](/.github/contributors/). The name of the file
+should be your GitHub username, with the extension `.md`. For example, the user
+example_user would create the file `.github/contributors/example_user.md`.
+
+Read this agreement carefully before signing. These terms and conditions
+constitute a binding legal agreement.
+
+## Contributor Agreement
+
+1. The term "contribution" or "contributed materials" means any source code,
+object code, patch, tool, sample, graphic, specification, manual,
+documentation, or any other material posted or submitted by you to the project.
+
+2. With respect to any worldwide copyrights, or copyright applications and
+registrations, in your contribution:
+
+    * you hereby assign to us joint ownership, and to the extent that such
+    assignment is or becomes invalid, ineffective or unenforceable, you hereby
+    grant to us a perpetual, irrevocable, non-exclusive, worldwide, no-charge,
+    royalty-free, unrestricted license to exercise all rights under those
+    copyrights. This includes, at our option, the right to sublicense these same
+    rights to third parties through multiple levels of sublicensees or other
+    licensing arrangements;
+
+    * you agree that each of us can do all things in relation to your
+    contribution as if each of us were the sole owners, and if one of us makes
+    a derivative work of your contribution, the one who makes the derivative
+    work (or has it made will be the sole owner of that derivative work;
+
+    * you agree that you will not assert any moral rights in your contribution
+    against us, our licensees or transferees;
+
+    * you agree that we may register a copyright in your contribution and
+    exercise all ownership rights associated with it; and
+
+    * you agree that neither of us has any duty to consult with, obtain the
+    consent of, pay or render an accounting to the other for any use or
+    distribution of your contribution.
+
+3. With respect to any patents you own, or that you can license without payment
+to any third party, you hereby grant to us a perpetual, irrevocable,
+non-exclusive, worldwide, no-charge, royalty-free license to:
+
+    * make, have made, use, sell, offer to sell, import, and otherwise transfer
+    your contribution in whole or in part, alone or in combination with or
+    included in any product, work or materials arising out of the project to
+    which your contribution was submitted, and
+
+    * at our option, to sublicense these same rights to third parties through
+    multiple levels of sublicensees or other licensing arrangements.
+
+4. Except as set out above, you keep all right, title, and interest in your
+contribution. The rights that you grant to us under these terms are effective
+on the date you first submitted a contribution to us, even if your submission
+took place before the date you sign these terms.
+
+5. You covenant, represent, warrant and agree that:
+
+    * Each contribution that you submit is and shall be an original work of
+    authorship and you can legally grant the rights set out in this SCA;
+
+    * to the best of your knowledge, each contribution will not violate any
+    third party's copyrights, trademarks, patents, or other intellectual
+    property rights; and
+
+    * each contribution shall be in compliance with U.S. export control laws and
+    other applicable export and import laws. You agree to notify us if you
+    become aware of any circumstance which would make any of the foregoing
+    representations inaccurate in any respect. We may publicly disclose your
+    participation in the project, including the fact that you have signed the SCA.
+
+6. This SCA is governed by the laws of the State of California and applicable
+U.S. Federal law. Any choice of law rules will not apply.
+
+7. Please place an “x” on one of the applicable statement below. Please do NOT
+mark both statements:
+
+    * [x] I am signing on behalf of myself as an individual and no other person
+    or entity, including my employer, has or will have rights with respect to my
+    contributions.
+
+    * [ ] I am signing on behalf of my employer or a legal entity and I have the
+    actual authority to contractually bind that entity.
+
+## Contributor Details
+
+| Field                          | Entry                |
+|------------------------------- | -------------------- |
+| Name                           |     Pamphile Roy     |
+| Company name (if applicable)   |         N/A          |
+| Title or role (if applicable)  |         N/A          |
+| Date                           | January 29th, 2021   |
+| GitHub username                |         tupui        |
+| Website (optional)             |         N/A          |
diff --git a/spacy/cli/download.py b/spacy/cli/download.py
index 5fcac63c0..6f9697f32 100644
--- a/spacy/cli/download.py
+++ b/spacy/cli/download.py
@@ -103,8 +103,6 @@ def download_model(
     filename: str, user_pip_args: Optional[Sequence[str]] = None
 ) -> None:
     download_url = about.__download_url__ + "/" + filename
-    pip_args = ["--no-cache-dir"]
-    if user_pip_args:
-        pip_args.extend(user_pip_args)
+    pip_args = user_pip_args if user_pip_args is not None else []
     cmd = [sys.executable, "-m", "pip", "install"] + pip_args + [download_url]
     run_command(cmd)
diff --git a/spacy/errors.py b/spacy/errors.py
index 6874f9a0c..f321b8c5a 100644
--- a/spacy/errors.py
+++ b/spacy/errors.py
@@ -483,6 +483,7 @@ class Errors:
     E199 = ("Unable to merge 0-length span at `doc[{start}:{end}]`.")
     E200 = ("Can't yet set {attr} from Span. Vote for this feature on the "
             "issue tracker: http://github.com/explosion/spaCy/issues")
+    E202 = ("Unsupported alignment mode '{mode}'. Supported modes: {modes}.")
 
     # TODO: fix numbering after merging develop into master
     E886 = ("Can't replace {name} -> {tok2vec} listeners: path '{path}' not "
diff --git a/spacy/tests/doc/test_span.py b/spacy/tests/doc/test_span.py
index 4c7f0c86b..078cc81b1 100644
--- a/spacy/tests/doc/test_span.py
+++ b/spacy/tests/doc/test_span.py
@@ -195,6 +195,12 @@ def test_spans_by_character(doc):
     assert span1.end_char == span2.end_char
     assert span2.label_ == "GPE"
 
+    # unsupported alignment mode
+    with pytest.raises(ValueError):
+        span2 = doc.char_span(
+            span1.start_char + 1, span1.end_char, label="GPE", alignment_mode="unk"
+        )
+
 
 def test_span_to_array(doc):
     span = doc[1:-2]
diff --git a/spacy/tokens/doc.pyx b/spacy/tokens/doc.pyx
index 489de2201..a40931720 100644
--- a/spacy/tokens/doc.pyx
+++ b/spacy/tokens/doc.pyx
@@ -525,8 +525,9 @@ cdef class Doc:
             label = self.vocab.strings.add(label)
         if not isinstance(kb_id, int):
             kb_id = self.vocab.strings.add(kb_id)
-        if alignment_mode not in ("strict", "contract", "expand"):
-            alignment_mode = "strict"
+        alignment_modes = ("strict", "contract", "expand")
+        if alignment_mode not in alignment_modes:
+            raise ValueError(Errors.E202.format(mode=alignment_mode, modes=", ".join(alignment_modes)))
         cdef int start = token_by_char(self.c, self.length, start_idx)
         if start < 0 or (alignment_mode == "strict" and start_idx != self[start].idx):
             return None