diff --git a/src/main/less/petclinic.less b/src/main/less/petclinic.less
index df43dfbb2..f94a59b07 100644
--- a/src/main/less/petclinic.less
+++ b/src/main/less/petclinic.less
@@ -250,16 +250,16 @@ table td.action-column {
 }
 
 .alert-success {
-  alert-variant(fade(@alert-success-bg, 70%); @alert-success-border; @alert-success-text);
+  @include alert-variant(fade(@alert-success-bg, 70%); @alert-success-border; @alert-success-text);
 }
 .alert-info {
-  alert-variant(fade(@alert-info-bg, 70%); @alert-info-border; @alert-info-text);
+  @include alert-variant(fade(@alert-info-bg, 70%); @alert-info-border; @alert-info-text);
 }
 .alert-warning {
-  alert-variant(fade(@alert-warning-bg, 70%); @alert-warning-border; @alert-warning-text);
+  @include alert-variant(fade(@alert-warning-bg, 70%); @alert-warning-border; @alert-warning-text);
 }
 .alert-danger {
-  alert-variant(fade(@alert-danger-bg, 70%); @alert-danger-border; @alert-danger-text);
+  @include alert-variant(fade(@alert-danger-bg, 70%); @alert-danger-border; @alert-danger-text);
 }
 
 .myspinner {