diff --git a/lib/oxsdatatypes/src/date_time.rs b/lib/oxsdatatypes/src/date_time.rs
index 63c45f0b..38508f66 100644
--- a/lib/oxsdatatypes/src/date_time.rs
+++ b/lib/oxsdatatypes/src/date_time.rs
@@ -188,8 +188,11 @@ impl DateTime {
             self.checked_sub_day_time_duration(rhs)
         } else {
             Some(Self {
-                timestamp: Timestamp::new(&date_time_plus_duration(-rhs, &self.properties())?)
-                    .ok()?,
+                timestamp: Timestamp::new(&date_time_plus_duration(
+                    rhs.checked_neg()?,
+                    &self.properties(),
+                )?)
+                .ok()?,
             })
         }
     }
diff --git a/lib/oxsdatatypes/src/decimal.rs b/lib/oxsdatatypes/src/decimal.rs
index 1b6fa6cc..73335f96 100644
--- a/lib/oxsdatatypes/src/decimal.rs
+++ b/lib/oxsdatatypes/src/decimal.rs
@@ -141,6 +141,14 @@ impl Decimal {
         })
     }
 
+    /// [op:numeric-unary-minus](https://www.w3.org/TR/xpath-functions/#func-numeric-unary-minus)
+    #[inline]
+    pub fn checked_neg(&self) -> Option<Self> {
+        Some(Self {
+            value: self.value.checked_neg()?,
+        })
+    }
+
     /// [fn:abs](https://www.w3.org/TR/xpath-functions/#func-abs)
     #[inline]
     pub const fn abs(&self) -> Self {
@@ -698,7 +706,10 @@ mod tests {
     fn add() {
         assert!(Decimal::MIN.checked_add(Decimal::STEP).is_some());
         assert!(Decimal::MAX.checked_add(Decimal::STEP).is_none());
-        assert_eq!(Decimal::MAX.checked_add(Decimal::MIN), Some(-Decimal::STEP));
+        assert_eq!(
+            Decimal::MAX.checked_add(Decimal::MIN),
+            Decimal::STEP.checked_neg()
+        );
     }
 
     #[test]
diff --git a/lib/oxsdatatypes/src/duration.rs b/lib/oxsdatatypes/src/duration.rs
index 0bc9d2bf..55fd6001 100644
--- a/lib/oxsdatatypes/src/duration.rs
+++ b/lib/oxsdatatypes/src/duration.rs
@@ -107,6 +107,14 @@ impl Duration {
         })
     }
 
+    #[inline]
+    pub fn checked_neg(&self) -> Option<Self> {
+        Some(Self {
+            year_month: self.year_month.checked_neg()?,
+            day_time: self.day_time.checked_neg()?,
+        })
+    }
+
     /// Checks if the two values are [identical](https://www.w3.org/TR/xmlschema11-2/#identity).
     #[inline]
     pub fn is_identical_with(&self, other: &Self) -> bool {
@@ -301,6 +309,13 @@ impl YearMonthDuration {
         })
     }
 
+    #[inline]
+    pub fn checked_neg(&self) -> Option<Self> {
+        Some(Self {
+            months: self.months.checked_neg()?,
+        })
+    }
+
     /// Checks if the two values are [identical](https://www.w3.org/TR/xmlschema11-2/#identity).
     #[inline]
     pub fn is_identical_with(&self, other: &Self) -> bool {
@@ -467,6 +482,13 @@ impl DayTimeDuration {
         })
     }
 
+    #[inline]
+    pub fn checked_neg(&self) -> Option<Self> {
+        Some(Self {
+            seconds: self.seconds.checked_neg()?,
+        })
+    }
+
     /// Checks if the two values are [identical](https://www.w3.org/TR/xmlschema11-2/#identity).
     #[inline]
     pub fn is_identical_with(&self, other: &Self) -> bool {
diff --git a/lib/oxsdatatypes/src/integer.rs b/lib/oxsdatatypes/src/integer.rs
index 46175fc3..0c9d90e5 100644
--- a/lib/oxsdatatypes/src/integer.rs
+++ b/lib/oxsdatatypes/src/integer.rs
@@ -73,6 +73,14 @@ impl Integer {
         })
     }
 
+    /// [op:numeric-unary-minus](https://www.w3.org/TR/xpath-functions/#func-numeric-unary-minus)
+    #[inline]
+    pub fn checked_neg(&self) -> Option<Self> {
+        Some(Self {
+            value: self.value.checked_neg()?,
+        })
+    }
+
     /// [fn:abs](https://www.w3.org/TR/xpath-functions/#func-abs)
     #[inline]
     pub const fn abs(&self) -> Self {
diff --git a/lib/src/sparql/eval.rs b/lib/src/sparql/eval.rs
index 4d2d738f..e92c66cf 100644
--- a/lib/src/sparql/eval.rs
+++ b/lib/src/sparql/eval.rs
@@ -1189,11 +1189,13 @@ impl SimpleEvaluator {
                 Rc::new(move |tuple| match e(tuple)? {
                     EncodedTerm::FloatLiteral(value) => Some((-value).into()),
                     EncodedTerm::DoubleLiteral(value) => Some((-value).into()),
-                    EncodedTerm::IntegerLiteral(value) => Some((-value).into()),
-                    EncodedTerm::DecimalLiteral(value) => Some((-value).into()),
-                    EncodedTerm::DurationLiteral(value) => Some((-value).into()),
-                    EncodedTerm::YearMonthDurationLiteral(value) => Some((-value).into()),
-                    EncodedTerm::DayTimeDurationLiteral(value) => Some((-value).into()),
+                    EncodedTerm::IntegerLiteral(value) => Some(value.checked_neg()?.into()),
+                    EncodedTerm::DecimalLiteral(value) => Some(value.checked_neg()?.into()),
+                    EncodedTerm::DurationLiteral(value) => Some(value.checked_neg()?.into()),
+                    EncodedTerm::YearMonthDurationLiteral(value) => {
+                        Some(value.checked_neg()?.into())
+                    }
+                    EncodedTerm::DayTimeDurationLiteral(value) => Some(value.checked_neg()?.into()),
                     _ => None,
                 })
             }