diff --git a/src/fromager/constraints.py b/src/fromager/constraints.py
index f81a9f6e..f41ac459 100644
--- a/src/fromager/constraints.py
+++ b/src/fromager/constraints.py
@@ -25,6 +25,11 @@ def add_constraint(self, unparsed: str) -> None:
         req = Requirement(unparsed)
         canon_name = canonicalize_name(req.name)
         previous = self._data.get(canon_name)
+
+        if not requirements_file.evaluate_marker(req, req):
+            logger.debug(f"Constraint {req} does not match environment")
+            return
+
         if previous is not None:
             raise KeyError(
                 f"{canon_name}: new constraint '{req}' conflicts with '{previous}'"
diff --git a/tests/test_constraints.py b/tests/test_constraints.py
index 6e0c96e0..f9253800 100644
--- a/tests/test_constraints.py
+++ b/tests/test_constraints.py
@@ -1,6 +1,8 @@
 import pathlib
+import typing
 
 import pytest
+from packaging import markers
 from packaging.requirements import Requirement
 from packaging.version import Version
 
@@ -37,15 +39,67 @@ def test_add_constraint_conflict():
     c = constraints.Constraints()
     c.add_constraint("foo<=1.1")
     c.add_constraint("flit_core==2.0rc3")
+
+    # Exact duplicate should raise error (same package, same marker)
     with pytest.raises(KeyError):
         c.add_constraint("foo<=1.1")
+
+    # Different version, same marker (no marker) should raise error
     with pytest.raises(KeyError):
         c.add_constraint("foo>1.1")
+
+    # Different version for flit_core should raise error
     with pytest.raises(KeyError):
         c.add_constraint("flit_core>2.0.0")
+
+    # Normalized name conflict should raise error
     with pytest.raises(KeyError):
         c.add_constraint("flit-core>2.0.0")
 
+    # Different, but equivalent markers should raise KeyError
+    with pytest.raises(KeyError):
+        c.add_constraint(
+            "bar==1.0; python_version >= '3.11' and platform_machine == 'x86_64'"
+        )
+        c.add_constraint(
+            "bar==1.1; platform_machine == 'x86_64' and python_version >= '3.11'"
+        )
+        c.add_constraint(
+            "bar==1.0; python_version >= '3.11' and platform_machine == 'arm64'"
+        )
+        c.add_constraint(
+            "bar==1.1; platform_machine == 'arm64' and python_version >= '3.11'"
+        )
+
+    # Same package with different markers should NOT raise error
+    c.add_constraint("baz==1.0; platform_machine != 'ppc64le'")
+    c.add_constraint("baz==1.1; platform_machine == 'ppc64le'")
+
+    # But same package with same marker should raise error
+    with pytest.raises(KeyError):
+        c.add_constraint("foo==1.2; platform_machine != 'ppc64le'")
+
+    # Verify multiple constraints for same package are stored
+    assert len(c._data) == 4  # flit_core, foo, bar, and baz
+
+    # Make sure correct constraint is added
+    env = typing.cast(dict[str, str], markers.default_environment())
+    constraint = c.get_constraint("bar")
+
+    if env.get("platform_machine") == "x86_64" and constraint is not None:
+        assert constraint.name == "bar"
+        assert constraint.specifier == "==1.0"
+        assert constraint.marker == markers.Marker(
+            'python_version >= "3.11" and platform_machine == "x86_64"'
+        )
+
+    if env.get("platform_machine") == "arm64" and constraint is not None:
+        assert constraint.name == "bar"
+        assert constraint.specifier == "==1.0"
+        assert constraint.marker == markers.Marker(
+            'python_version >= "3.11" and platform_machine == "arm64"'
+        )
+
 
 def test_allow_prerelease():
     c = constraints.Constraints()