diff --git a/src/verification.ml b/src/verification.ml
index a503536e51537f0dbb462bf933039141fa5de11c..d91151d453f1cb53b6bbb6b9b8482bba54fea576 100644
--- a/src/verification.ml
+++ b/src/verification.ml
@@ -108,7 +108,7 @@ let answer_saver limit config env config_prover dataset task =
         then filename
         else
           invalid_arg
-            (Fmt.str "File '%s' has an unsupported  extension" filename)
+            (Fmt.str "File '%s' has an unsupported extension" filename)
     in
     Dataset.interpret_predicate env ~on_model ~on_dataset task
   in