diff --git a/R/coord-.r b/R/coord-.r
index 17fb57602f..ce60824963 100644
--- a/R/coord-.r
+++ b/R/coord-.r
@@ -87,6 +87,8 @@ Coord <- ggproto("Coord",
 
   is_linear = function() FALSE,
 
+  # Does the coordinate system support free scaling of axes in a faceted plot?
+  # Will generally have to return FALSE for coordinate systems that enforce a fixed aspect ratio.
   is_free = function() FALSE,
 
   setup_params = function(data) {
diff --git a/R/sf.R b/R/sf.R
index 9d1e45cb3e..e8e87e0e37 100644
--- a/R/sf.R
+++ b/R/sf.R
@@ -353,6 +353,9 @@ CoordSf <- ggproto("CoordSf", CoordCartesian,
     )
   },
 
+  # CoordSf enforces a fixed aspect ratio -> axes cannot be changed freely under faceting
+  is_free = function() FALSE,
+
   aspect = function(self, panel_params) {
     if (isTRUE(sf::st_is_longlat(panel_params$crs))) {
       # Contributed by @edzer