diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9a9b7442..09bf3486 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,10 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
 - Fixed a regression in quoting of pip arguments introduced in
   [#185](https://github.com/pyodide/pyodide-build/pull/185).
   [#209](https://github.com/pyodide/pyodide-build/pull/209)
 
+- `pyodide-build` now correctly works with file paths with spaces passed to the `PIP_CONSTRAINT` environment variable.
+  [#210](https://github.com/pyodide/pyodide-build/pull/210)
+
 ## [0.30.4] - 2025/05/20
 
 - Fixed compatibility with `virtualenv` 20.31 and later. The Pyodide virtual environment via `pyodide venv` no longer seeds
diff --git a/pyodide_build/build_env.py b/pyodide_build/build_env.py
index 4a13080b..508d273c 100644
--- a/pyodide_build/build_env.py
+++ b/pyodide_build/build_env.py
@@ -15,6 +15,7 @@
 
 from pyodide_build import __version__
 from pyodide_build.common import default_xbuildenv_path, search_pyproject_toml, to_bool
+from pyodide_build.logger import logger
 
 RUST_BUILD_PRELUDE = """
 rustup default ${RUST_TOOLCHAIN}
@@ -334,10 +335,16 @@ def _create_constraints_file() -> str:
     if not constraints:
         return ""
 
-    if len(constraints.split(maxsplit=1)) > 1:
-        raise ValueError(
-            "PIP_CONSTRAINT contains spaces so pip will misinterpret it. Make sure the path to pyodide has no spaces.\n"
-            "See https://github.com/pypa/pip/issues/13283"
+    # If a path to a file specified PIP_CONSTRAINT contains spaces, pip will misinterpret
+    # it as multiple files; see https://github.com/pypa/pip/issues/13283. This is fine if
+    # the user wants to use multiple constraints files, but if they use a single file, we
+    # warn them about it and ask to convert the path to a URI or to remove spaces in it.
+    if " " in constraints:
+        logger.info(
+            "The value of PIP_CONSTRAINT contains spaces, and pip will interpret it as "
+            "multiple files. If you are using a single constraints file and it has spaces "
+            "in its file path, please convert it to a URI instead. Please ignore this "
+            "message if you are using multiple constraints files."
         )
 
     constraints_file = Path(constraints)
diff --git a/pyodide_build/recipe/builder.py b/pyodide_build/recipe/builder.py
index 8b6885ad..e2f15fbc 100755
--- a/pyodide_build/recipe/builder.py
+++ b/pyodide_build/recipe/builder.py
@@ -136,11 +136,17 @@ def __init__(
         self.build_dir = (
             Path(build_dir).resolve() if build_dir else self.pkg_root / "build"
         )
-        if len(str(self.build_dir).split(maxsplit=1)) > 1:
-            raise ValueError(
-                "PIP_CONSTRAINT contains spaces so pip will misinterpret it. Make sure the path to the package build directory has no spaces.\n"
-                "See https://github.com/pypa/pip/issues/13283"
+        # If a path to a file specified PIP_CONSTRAINT contains spaces, pip will misinterpret
+        # it as multiple files; see https://github.com/pypa/pip/issues/13283
+        # We work around this by converting the path to a URI when needed.
+        if " " in str(self.build_dir):
+            logger.info(
+                "The value of PIP_CONSTRAINT contains spaces, and pip will interpret it as "
+                "multiple files. If you are using a single constraints file and it has spaces "
+                "in its file path, please convert it to a URI instead. Please ignore this "
+                "message if you are using multiple constraints files."
             )
+
         self.library_install_prefix = self.build_dir.parent.parent / ".libs"
         self.src_extract_dir = (
             self.build_dir / self.fullname
@@ -367,7 +373,7 @@ def _download_and_extract(self) -> None:
         shutil.move(self.build_dir / extract_dir_name, self.src_extract_dir)
         self.src_dist_dir.mkdir(parents=True, exist_ok=True)
 
-    def _create_constraints_file(self) -> str:
+    def _create_combined_constraints_file(self) -> str:
         """
         Creates a pip constraints file by concatenating global constraints (PIP_CONSTRAINT)
         with constraints specific to this package.
@@ -434,7 +440,7 @@ def _compile(
                     )
                     build_env = runner.env
 
-            build_env["PIP_CONSTRAINT"] = str(self._create_constraints_file())
+            build_env["PIP_CONSTRAINT"] = str(self._create_combined_constraints_file())
 
             wheel_path = pypabuild.build(
                 self.src_extract_dir, self.src_dist_dir, build_env, config_settings
diff --git a/pyodide_build/tests/recipe/test_builder.py b/pyodide_build/tests/recipe/test_builder.py
index ba80a027..aa649802 100644
--- a/pyodide_build/tests/recipe/test_builder.py
+++ b/pyodide_build/tests/recipe/test_builder.py
@@ -183,7 +183,7 @@ def test_create_constraints_file_no_override(tmp_path, dummy_xbuildenv):
         build_dir=tmp_path,
     )
 
-    path = builder._create_constraints_file()
+    path = builder._create_combined_constraints_file()
     assert path == get_build_flag("PIP_CONSTRAINT")
 
 
@@ -194,7 +194,7 @@ def test_create_constraints_file_override(tmp_path, dummy_xbuildenv):
         build_dir=tmp_path,
     )
 
-    paths = builder._create_constraints_file()
+    paths = builder._create_combined_constraints_file()
     assert paths == get_build_flag("PIP_CONSTRAINT") + " " + str(
         tmp_path / "constraints.txt"
     )
diff --git a/pyodide_build/tests/test_cli.py b/pyodide_build/tests/test_cli.py
index 743a26f4..14e328fb 100644
--- a/pyodide_build/tests/test_cli.py
+++ b/pyodide_build/tests/test_cli.py
@@ -72,7 +72,7 @@ def test_skeleton_pypi(tmp_path):
         skeleton.app, ["pypi", test_pkg, "--recipe-dir", str(tmp_path)]
     )
     assert result.exit_code != 0
-    assert "already exists" in str(result.stdout)
+    assert "already exists" in str(result.stderr)
     assert isinstance(result.exception, SystemExit)