diff --git a/lib/matplotlib/backends/registry.py b/lib/matplotlib/backends/registry.py
index 3c85a9b47d7b..7f5a53f917a4 100644
--- a/lib/matplotlib/backends/registry.py
+++ b/lib/matplotlib/backends/registry.py
@@ -407,7 +407,7 @@ def resolve_gui_or_backend(self, gui_or_backend):
             return self.resolve_backend(gui_or_backend)
         except Exception:  # KeyError ?
             raise RuntimeError(
-                f"'{gui_or_backend} is not a recognised GUI loop or backend name")
+                f"'{gui_or_backend}' is not a recognised GUI loop or backend name")
 
 
 # Singleton