diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index 8bf783020b..005a52b675 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -2034,7 +2034,7 @@ stcsign:
     // add characters at the separate marker (if there is one) to
     // fill up the available space.
   } else if (width < maxwidth
-             && outputlen + (size_t)(maxwidth - width) + 1 < outlen) {
+             && outputlen + (size_t)(maxwidth - width) * schar_len(fillchar) + 1 < outlen) {
     // Find how many separators there are, which we will use when
     // figuring out how many groups there are.
     int num_separators = 0;
diff --git a/test/unit/statusline_spec.lua b/test/unit/statusline_spec.lua
index a97a4f41d7..1388063a92 100644
--- a/test/unit/statusline_spec.lua
+++ b/test/unit/statusline_spec.lua
@@ -12,7 +12,7 @@ local stl = t.cimport('./src/nvim/statusline.h')
 local grid = t.cimport('./src/nvim/grid.h')
 
 describe('build_stl_str_hl', function()
-  local buffer_byte_size = 100
+  local buffer_byte_size = 120
   local STL_INITIAL_ITEMS = 20
   local output_buffer = ''