diff --git a/pkg/hints/usort_hints.go b/pkg/hints/usort_hints.go
index 3d0a5d75..ba1d0c67 100644
--- a/pkg/hints/usort_hints.go
+++ b/pkg/hints/usort_hints.go
@@ -3,6 +3,7 @@ package hints
 import (
 	"github.com/lambdaclass/cairo-vm.go/pkg/lambdaworks"
 	"github.com/lambdaclass/cairo-vm.go/pkg/types"
+	"github.com/pkg/errors"
 )
 
 // Implements hint:
@@ -10,7 +11,11 @@ import (
 func usort_enter_scope(executionScopes *types.ExecutionScopes) error {
 	usort_max_size, err := executionScopes.Get("usort_max_size")
 
-	usort_max_size_felt := usort_max_size.(lambdaworks.Felt)
+	usort_max_size_felt, cast_ok := usort_max_size.(lambdaworks.Felt)
+
+	if !cast_ok {
+		return errors.New("Error casting usort_max_size into a Felt")
+	}
 
 	if err != nil {
 		return err