diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
index 17650de2b8..4302c9a58b 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/AbstractOperations.cpp
@@ -321,33 +321,21 @@ ThrowCompletionOr<u64> to_temporal_rounding_increment(GlobalObject& global_objec
 // 13.13 ToTemporalDateTimeRoundingIncrement ( normalizedOptions, smallestUnit ), https://tc39.es/proposal-temporal/#sec-temporal-totemporaldatetimeroundingincrement
 ThrowCompletionOr<u64> to_temporal_date_time_rounding_increment(GlobalObject& global_object, Object const& normalized_options, StringView smallest_unit)
 {
-    double maximum;
+    u16 maximum;
 
     // 1. If smallestUnit is "day", then
     if (smallest_unit == "day"sv) {
         // a. Let maximum be 1.
         maximum = 1;
     }
-    // 2. Else if smallestUnit is "hour", then
-    else if (smallest_unit == "hour"sv) {
-        // a. Let maximum be 24.
-        maximum = 24;
-    }
-    // 3. Else if smallestUnit is "minute" or "second", then
-    else if (smallest_unit.is_one_of("minute"sv, "second"sv)) {
-        // a. Let maximum be 60.
-        maximum = 60;
-    }
-    // 4. Else,
+    // 2. Else,
     else {
-        // a. Assert: smallestUnit is "millisecond", "microsecond", or "nanosecond".
-        VERIFY(smallest_unit.is_one_of("millisecond"sv, "microsecond"sv, "nanosecond"sv));
-
-        // b. Let maximum be 1000.
-        maximum = 1000;
+        // a. Let maximum be ! MaximumTemporalDurationRoundingIncrement(smallestUnit).
+        // b. Assert: maximum is not undefined.
+        maximum = *maximum_temporal_duration_rounding_increment(smallest_unit);
     }
 
-    // 5. Return ? ToTemporalRoundingIncrement(normalizedOptions, maximum, false).
+    // 3. Return ? ToTemporalRoundingIncrement(normalizedOptions, maximum, false).
     return to_temporal_rounding_increment(global_object, normalized_options, maximum, false);
 }
 
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainTimePrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainTimePrototype.cpp
index c07feab515..f542effa6b 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainTimePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainTimePrototype.cpp
@@ -299,31 +299,16 @@ JS_DEFINE_NATIVE_FUNCTION(PlainTimePrototype::round)
     // 7. Let roundingMode be ? ToTemporalRoundingMode(roundTo, "halfExpand").
     auto rounding_mode = TRY(to_temporal_rounding_mode(global_object, *round_to, "halfExpand"));
 
-    double maximum;
+    // 8. Let maximum be ! MaximumTemporalDurationRoundingIncrement(smallestUnit).
+    auto maximum = maximum_temporal_duration_rounding_increment(*smallest_unit);
 
-    // 8. If smallestUnit is "hour", then
-    if (smallest_unit == "hour"sv) {
-        // a. Let maximum be 24.
-        maximum = 24;
-    }
-    // 9. Else if smallestUnit is "minute" or "second", then
-    else if (smallest_unit == "minute"sv || smallest_unit == "second"sv) {
-        // a. Let maximum be 60.
-        maximum = 60;
-    }
-    // 10. Else,
-    else {
-        // a. Let maximum be 1000.
-        maximum = 1000;
-    }
+    // 9. Let roundingIncrement be ? ToTemporalRoundingIncrement(roundTo, maximum, false).
+    auto rounding_increment = TRY(to_temporal_rounding_increment(global_object, *round_to, *maximum, false));
 
-    // 11. Let roundingIncrement be ? ToTemporalRoundingIncrement(roundTo, maximum, false).
-    auto rounding_increment = TRY(to_temporal_rounding_increment(global_object, *round_to, maximum, false));
-
-    // 12. Let result be ! RoundTime(temporalTime.[[ISOHour]], temporalTime.[[ISOMinute]], temporalTime.[[ISOSecond]], temporalTime.[[ISOMillisecond]], temporalTime.[[ISOMicrosecond]], temporalTime.[[ISONanosecond]], roundingIncrement, smallestUnit, roundingMode).
+    // 10. Let result be ! RoundTime(temporalTime.[[ISOHour]], temporalTime.[[ISOMinute]], temporalTime.[[ISOSecond]], temporalTime.[[ISOMillisecond]], temporalTime.[[ISOMicrosecond]], temporalTime.[[ISONanosecond]], roundingIncrement, smallestUnit, roundingMode).
     auto result = round_time(temporal_time->iso_hour(), temporal_time->iso_minute(), temporal_time->iso_second(), temporal_time->iso_millisecond(), temporal_time->iso_microsecond(), temporal_time->iso_nanosecond(), rounding_increment, *smallest_unit, rounding_mode);
 
-    // 13. Return ? CreateTemporalTime(result.[[Hour]], result.[[Minute]], result.[[Second]], result.[[Millisecond]], result.[[Microsecond]], result.[[Nanosecond]]).
+    // 11. Return ? CreateTemporalTime(result.[[Hour]], result.[[Minute]], result.[[Second]], result.[[Millisecond]], result.[[Microsecond]], result.[[Nanosecond]]).
     return TRY(create_temporal_time(global_object, result.hour, result.minute, result.second, result.millisecond, result.microsecond, result.nanosecond));
 }