diff --git a/styles/components/registrationForm.less b/styles/components/registrationForm.less
index 6f20b4d..c5143d9 100644
--- a/styles/components/registrationForm.less
+++ b/styles/components/registrationForm.less
@@ -123,7 +123,7 @@ fieldset {
 .form-control {
     all: revert;
     padding: 0.5em;
-    width: calc(100% - 0.5em * 2); /* Would be better to use custom properties, but crashed CSS processing (#51) */
+    width: ~"calc(100% - 0.5em * 2)"; /* Would be better to use custom properties, but crashed CSS processing (#51) */
     border-color: lightgrey;
     border: 1px solid #ced4da;
     border-radius: 0.3em;