diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp
index 7996692ff8..a32ec83ae9 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonth.cpp
@@ -180,7 +180,7 @@ ISOYearMonth balance_iso_year_month(double year, double month)
     year += floor((month - 1) / 12);
 
     // 3. Set month to (month − 1) modulo 12 + 1.
-    month = fmod(month - 1, 12) + 1;
+    month = modulo(month - 1, 12.0) + 1;
 
     // 4. Return the Record { [[Year]]: year, [[Month]]: month }.
     return ISOYearMonth { .year = static_cast<i32>(year), .month = static_cast<u8>(month), .reference_iso_day = 0 };