diff --git a/aerich/inspect/__init__.py b/aerich/inspect/__init__.py
index ee7fd1b..1b7f8db 100644
--- a/aerich/inspect/__init__.py
+++ b/aerich/inspect/__init__.py
@@ -36,7 +36,7 @@ class Column(BaseModel):
                 length_parts.append(f"max_digits={self.max_digits}")
             if self.decimal_places:
                 length_parts.append(f"decimal_places={self.decimal_places}")
-            length = "".join(length_parts)
+            length = ",".join(length_parts)
         if self.null:
             null = "null=True, "
         if self.default is not None: