diff --git a/lockfile/src/parsers/pypi.rs b/lockfile/src/parsers/pypi.rs
index 8eb996a05..d3cd1ac20 100644
--- a/lockfile/src/parsers/pypi.rs
+++ b/lockfile/src/parsers/pypi.rs
@@ -55,13 +55,17 @@ fn line<'a>(input: &'a str, registry: &mut Option<&'a str>) -> IResult<&'a str,
 
     // Ignore index config options.
     //
-    // Since `ThirdPartyVersion` only allows a single registry, we only record the
-    // primary one.
+    // Since `ThirdPartyVersion` only allows a single registry, we prefer recording
+    // only the primary one.
     if let Some(index_url) = line.strip_prefix("--index-url") {
         *registry = Some(index_url.trim());
         line = "";
     }
-    if line.starts_with("--extra-index-url") {
+    if let Some(extra_index_url) = line.strip_prefix("--extra-index-url") {
+        // Only use extra index URL if no other URL has been specified.
+        if registry.is_none() {
+            *registry = Some(extra_index_url.trim());
+        }
         line = "";
     }