diff --git a/src/poetry/version/version_selector.py b/src/poetry/version/version_selector.py
index d40fcc7953a..342b7649ca3 100644
--- a/src/poetry/version/version_selector.py
+++ b/src/poetry/version/version_selector.py
@@ -32,7 +32,7 @@ def find_best_candidate(
             package_name,
             {
                 "version": target_package_version or "*",
-                "allow_prereleases": allow_prereleases,
+                "allow-prereleases": allow_prereleases,
                 "source": source,
             },
         )
diff --git a/tests/helpers.py b/tests/helpers.py
index 31233b827b9..08eb045baba 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -54,7 +54,7 @@ def get_dependency(
         constraint = {"version": constraint}
 
     constraint["optional"] = optional
-    constraint["allow_prereleases"] = allows_prereleases
+    constraint["allow-prereleases"] = allows_prereleases
 
     return Factory.create_dependency(name, constraint or "*", groups=groups)