diff --git a/Lib/gftools/builder/recipeproviders/googlefonts.py b/Lib/gftools/builder/recipeproviders/googlefonts.py
index 350328c9..d67e6425 100644
--- a/Lib/gftools/builder/recipeproviders/googlefonts.py
+++ b/Lib/gftools/builder/recipeproviders/googlefonts.py
@@ -218,7 +218,7 @@ def fix_args(self):
         if self.config.get("fvarInstanceAxisDflts"):
             args += (
                 " --fvar-instance-axis-dflts '"
-                + self.config["fvarInstanceAxisDflts"]
+                + " ".join([f"{k}={v}" for k, v in self.config["fvarInstanceAxisDflts"].items()])
                 + "'"
             )
         return args