diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index d4f60ea3..fe386d1e 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -223,6 +223,7 @@ public:
   constexpr quantity& operator/=(const Rep2& rhs)
     requires requires(rep a, const Rep2 b) { { a /= b } -> std::same_as<rep&>; }
   {
+    gsl_ExpectsAudit(rhs != quantity_values<Rep2>::zero());
     value_ /= rhs;
     return *this;
   }
@@ -230,6 +231,7 @@ public:
   constexpr quantity& operator/=(const dimensionless<units::one, Rep2>& rhs)
     requires requires(rep a, const Rep2 b) { { a /= b } -> std::same_as<rep&>; }
   {
+    gsl_ExpectsAudit(rhs.count() != quantity_values<Rep2>::zero());
     value_ /= rhs.count();
     return *this;
   }
@@ -239,6 +241,7 @@ public:
     requires (!floating_point_<rep>) && (!floating_point_<Rep2>) &&
              requires(rep a, const Rep2 b) { { a %= b } -> std::same_as<rep&>; }
   {
+    gsl_ExpectsAudit(rhs != quantity_values<Rep2>::zero());
     value_ %= rhs;
     return *this;
   }
@@ -247,6 +250,7 @@ public:
     requires (!floating_point_<rep>) &&
              requires(rep a, rep b) { { a %= b } -> std::same_as<rep&>; }
   {
+    gsl_ExpectsAudit(q.count() != quantity_values<rep>::zero());
     value_ %= q.count();
     return *this;
   }
@@ -328,6 +332,7 @@ public:
             invoke_result_convertible_to_<rep, std::modulus<>, rep, const Value&>
   [[nodiscard]] friend constexpr Quantity auto operator%(const quantity& q, const Value& v)
   {
+    gsl_ExpectsAudit(v != quantity_values<Value>::zero());
     using ret = quantity<D, U, std::invoke_result_t<std::modulus<>, rep, Value>>;
     return ret(q.count() % v);
   }
@@ -336,6 +341,7 @@ public:
     requires (!floating_point_<rep>) && is_same_v<unit, units::one> &&
             invoke_result_convertible_to_<rep, std::modulus<>, rep, rep>
   {
+    gsl_ExpectsAudit(rhs.count() != quantity_values<rep>::zero());
     return units::quantity(lhs.count() % rhs.count());
   }
 
@@ -402,6 +408,7 @@ template<typename D1, typename U1, typename Rep1, typename U2, typename Rep2>
           quantity_value_for_<std::modulus<>, Rep1, Rep2>
 [[nodiscard]] constexpr Quantity auto operator%(const quantity<D1, U1, Rep1>& lhs, const quantity<dim_one, U2, Rep2>& rhs)
 {
+  gsl_ExpectsAudit(rhs.count() != quantity_values<Rep2>::zero());
   using unit = downcast_unit<D1, U1::ratio * U2::ratio>;
   using ret = quantity<D1, unit, std::invoke_result_t<std::modulus<>, Rep1, Rep2>>;
   return ret(lhs.count() % rhs.count());
@@ -412,6 +419,7 @@ template<Quantity Q1, QuantityEquivalentTo<Q1> Q2>
           quantity_value_for_<std::modulus<>, typename Q1::rep, typename Q2::rep>
 [[nodiscard]] constexpr Quantity auto operator%(const Q1& lhs, const Q2& rhs)
 {
+  gsl_ExpectsAudit(rhs.count() != quantity_values<typename Q2::rep>::zero());
   using ret = common_quantity_for<std::modulus<>, Q1, Q2>;
   return ret(ret(lhs).count() % ret(rhs).count());
 }
diff --git a/src/include/units/quantity_kind.h b/src/include/units/quantity_kind.h
index 71b968b1..e8ec9fb5 100644
--- a/src/include/units/quantity_kind.h
+++ b/src/include/units/quantity_kind.h
@@ -185,6 +185,7 @@ public:
   constexpr quantity_kind& operator/=(const Rep2& rhs)
     requires requires(quantity_type q) { q /= rhs; }
   {
+    gsl_ExpectsAudit(rhs != quantity_values<Rep2>::zero());
     q_ /= rhs;
     return *this;
   }
@@ -193,6 +194,7 @@ public:
   constexpr quantity_kind& operator%=(const Rep2& rhs)
     requires (!Quantity<Rep2>) && requires(quantity_type q, const Rep2 r) { q %= r; }
   {
+    gsl_ExpectsAudit(rhs != quantity_values<Rep2>::zero());
     q_ %= rhs;
     return *this;
   }
@@ -200,6 +202,7 @@ public:
   constexpr quantity_kind& operator%=(const quantity_kind& qk)
     requires requires(quantity_type q) { q %= qk.common(); }
   {
+    gsl_ExpectsAudit(qk.common().count() != quantity_values<rep>::zero());
     q_ %= qk.common();
     return *this;
   }
@@ -224,6 +227,7 @@ public:
   [[nodiscard]] friend constexpr QuantityKind auto operator/(const quantity_kind& qk, const Value& v)
     requires requires { { qk.common() / v } -> Quantity; }
   {
+    gsl_ExpectsAudit(v != quantity_values<Value>::zero());
     return detail::make_quantity_kind<quantity_kind>(qk.common() / v);
   }
 
@@ -231,6 +235,7 @@ public:
   [[nodiscard]] friend constexpr QuantityKind auto operator/(const Value& v, const quantity_kind& qk)
     requires requires { { v / qk.common() } -> Quantity; }
   {
+    gsl_ExpectsAudit(qk.common().count() != quantity_values<rep>::zero());
     return detail::downcasted_kind<quantity_kind>(v / qk.common());
   }
 
@@ -238,6 +243,7 @@ public:
   [[nodiscard]] friend constexpr QuantityKind auto operator%(const quantity_kind& qk, const Value& v)
     requires requires { qk.common() % v; }
   {
+    gsl_ExpectsAudit(v != quantity_values<Value>::zero());
     return detail::make_quantity_kind<quantity_kind>(qk.common() % v);
   }
 
@@ -285,6 +291,7 @@ template<QuantityKind QK, Quantity Q>
 [[nodiscard]] constexpr QuantityKind auto operator/(const QK& lhs, const Q& rhs)
   requires requires { lhs.common() / rhs; }
 {
+  gsl_ExpectsAudit(rhs.count() != quantity_values<typename Q::rep>::zero());
   return detail::downcasted_kind<QK>(lhs.common() / rhs);
 }
 
@@ -292,6 +299,7 @@ template<Quantity Q, QuantityKind QK>
 [[nodiscard]] constexpr QuantityKind auto operator/(const Q& lhs, const QK& rhs)
   requires requires { lhs / rhs.common(); }
 {
+  gsl_ExpectsAudit(rhs.common().count() != quantity_values<typename QK::rep>::zero());
   return detail::downcasted_kind<QK>(lhs / rhs.common());
 }
 
@@ -299,6 +307,7 @@ template<QuantityKind QK, Dimensionless D>
 [[nodiscard]] constexpr QuantityKind auto operator%(const QK& lhs, const D& rhs)
   requires requires { lhs.common() % rhs; }
 {
+  gsl_ExpectsAudit(rhs.count() != quantity_values<typename D::rep>::zero());
   return detail::make_quantity_kind<QK>(lhs.common() % rhs);
 }
 
@@ -306,6 +315,7 @@ template<QuantityKind QK1, QuantityKindEquivalentTo<QK1> QK2>
 [[nodiscard]] constexpr QuantityKind auto operator%(const QK1& lhs, const QK2& rhs)
   requires requires { lhs.common() % rhs.common(); }
 {
+  gsl_ExpectsAudit(rhs.common().count() != quantity_values<typename QK2::rep>::zero());
   return detail::make_quantity_kind<QK1>(lhs.common() % rhs.common());
 }