diff --git a/pulp_rust/app/utils.py b/pulp_rust/app/utils.py
index 70a4fc5..07c32d7 100644
--- a/pulp_rust/app/utils.py
+++ b/pulp_rust/app/utils.py
@@ -37,6 +37,9 @@ def _normalize_req(version_str):
     return f"^{version_str}"
 
 
+CRATES_IO_INDEX = "https://github.com/rust-lang/crates.io-index"
+
+
 def parse_dep(name, spec, kind="normal", target=None):
     """Convert a single Cargo.toml dependency entry to index format."""
     if isinstance(spec, str):
@@ -49,7 +52,7 @@ def parse_dep(name, spec, kind="normal", target=None):
             "default_features": True,
             "target": target,
             "kind": kind,
-            "registry": None,
+            "registry": CRATES_IO_INDEX,
             "package": None,
         }
 
@@ -62,7 +65,7 @@ def parse_dep(name, spec, kind="normal", target=None):
         "default_features": spec.get("default-features", True),
         "target": target,
         "kind": kind,
-        "registry": spec.get("registry"),
+        "registry": spec.get("registry-index") or CRATES_IO_INDEX,
         "package": None,
     }
     # If the dep was renamed, "name" in the index is the alias (the key),
diff --git a/pulp_rust/tests/unit/test_utils.py b/pulp_rust/tests/unit/test_utils.py
index 086fbee..f59d017 100644
--- a/pulp_rust/tests/unit/test_utils.py
+++ b/pulp_rust/tests/unit/test_utils.py
@@ -10,6 +10,7 @@
 django.setup()
 
 from pulp_rust.app.utils import (  # noqa: E402
+    CRATES_IO_INDEX,
     canonicalize_crate_name,
     extract_cargo_toml,
     extract_dependencies,
@@ -44,7 +45,7 @@ def test_simple_string_spec(self):
             "default_features": True,
             "target": None,
             "kind": "normal",
-            "registry": None,
+            "registry": CRATES_IO_INDEX,
             "package": None,
         }
 
@@ -63,7 +64,7 @@ def test_table_spec_all_fields(self):
             "features": ["derive", "std"],
             "optional": True,
             "default-features": False,
-            "registry": "https://my-registry.example.com/",
+            "registry-index": "https://my-registry.example.com/",
             "package": "serde_real",
         }
         result = parse_dep("my_serde", spec)
@@ -75,6 +76,21 @@ def test_table_spec_all_fields(self):
         assert result["registry"] == "https://my-registry.example.com/"
         assert result["package"] == "serde_real"
 
+    def test_string_spec_registry_is_crates_io(self):
+        assert parse_dep("serde", "1.0")["registry"] == CRATES_IO_INDEX
+
+    def test_table_spec_without_registry_defaults_to_crates_io(self):
+        result = parse_dep("serde", {"version": "1.0"})
+        assert result["registry"] == CRATES_IO_INDEX
+
+    def test_table_spec_registry_index_preserved(self):
+        result = parse_dep("foo", {"version": "1.0", "registry-index": "https://r.example/"})
+        assert result["registry"] == "https://r.example/"
+
+    def test_table_spec_registry_name_is_ignored(self):
+        result = parse_dep("foo", {"version": "1.0", "registry": "my-named-registry"})
+        assert result["registry"] == CRATES_IO_INDEX
+
     def test_table_spec_no_version_defaults_to_star(self):
         result = parse_dep("foo", {"optional": True})
         assert result["req"] == "*"