diff --git a/nix/build-all.py b/nix/build-all.py
index d9a67bd99e..7e7791cc64 100644
--- a/nix/build-all.py
+++ b/nix/build-all.py
@@ -532,7 +532,7 @@ BUILD_STATIC = not ARGS.shared
 ENABLE_FLAG = "--enable-static" if BUILD_STATIC else "--enable-shared"
 DISABLE_FLAG = "--disable-shared" if BUILD_STATIC else "--disable-static"
 LINK_TYPE = "static" if BUILD_STATIC else "shared"
-LIBRARY_EXT = "a" if BUILD_STATIC else "so"
+LIBRARY_EXT = "a" if BUILD_STATIC else ("dylib" if APPLE else "so")
 PIC = "-fPIC" if BUILD_STATIC else ""
 
 if DYNAMIC_ARGS.py_versions: