diff --git a/poetry/repositories/installed_repository.py b/poetry/repositories/installed_repository.py
index 8e2fb7bae79..a4a58b546de 100644
--- a/poetry/repositories/installed_repository.py
+++ b/poetry/repositories/installed_repository.py
@@ -16,7 +16,8 @@ def load(cls, env):  # type: (Env) -> InstalledRepository
         """
         repo = cls()
 
-        freeze_output = env.run("pip", "freeze")
+        freeze_output = env.run("python", "-m", "pip", "freeze")
+
         for line in freeze_output.split("\n"):
             if "==" in line:
                 name, version = re.split("={2,3}", line)