diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 0dd54f7..487bf58 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -39,6 +39,7 @@
                 "files.autoSaveDelay": 1000,
                 "git.autofetch": true,
                 "python.analysis.extraPaths": [".devcontainer/ehrql-main/"],
+                "python.defaultInterpreterPath": "/opt/venv/bin/python3.10",
                 "python.terminal.activateEnvironment": true,
                 "python.terminal.activateEnvInCurrentTerminal": true,
                 "window.autoDetectColorScheme": true