diff --git a/README.md b/README.md
index ea5e4da..8b8e69d 100644
--- a/README.md
+++ b/README.md
@@ -197,10 +197,10 @@ $ Rscript -e bspm:::scripts mass_move --run user1 [user2 ...] [lib1 [lib2 ...]]
 New backends for other package managers can be added to `inst/service/backend`.
 Each backend must implement the following functions:
 
-- `def discover() -> dict({ "prefixes" : list, "exclusions" : list })`
-- `def available(prefixes : list, exclusions : list) -> list`
-- `def install(prefixes : list, pkgs : list, exclusions : list) -> list`
-- `def remove(prefixes : list, pkgs : list, exclusions : list) -> list`
+- `def discover() -> dict({ "prefixes": list, "exclusions": list })`
+- `def available(prefixes: list, exclusions: list) -> list`
+- `def install(prefixes: list, pkgs: list, exclusions: list, weak_deps: Optional[bool]=None) -> list`
+- `def remove(prefixes: list, pkgs: list, exclusions: list) -> list`
 
 The last two functions receive a list of prefixes, a list of R package names and
 a list of exclusions, and must return a list with those package names that could