diff --git a/doc/DESIGN.md b/doc/DESIGN.md
index 774c1995..6d2b73bf 100644
--- a/doc/DESIGN.md
+++ b/doc/DESIGN.md
@@ -377,12 +377,17 @@ public:
 Additional functions provide the support for operations that result in a different dimension type
 than those of their arguments.
 
-Another change comparing to `std::chrono::duration` is that the `duration` is using
-`std::common_type_t<Rep1, Rep2>` to find a common representation for a calculation result. Such
-a design was reported as problematic by numerics study group members as sometimes we want to provide
-a different type in case of multiplication and different in case of division. `std::common_type` lacks
-that additional information. That is why `units::quantity` uses the resulting type of a concrete operator
-operation and provides it directly to `units::common_quantity_t` type trait.
+Beside adding new elements a few other changes where applied compared to the `std::chrono::duration` class:
+1. The `duration` is using `std::common_type_t<Rep1, Rep2>` to find a common representation
+    for a calculation result. Such a design was reported as problematic by numerics study group members
+    as sometimes we want to provide a different type in case of multiplication and different in case of
+    division. `std::common_type` lacks that additional information. That is why `units::quantity` uses
+    the resulting type of a concrete operator operation and provides it directly to `units::common_quantity_t`
+    type trait.
+2. `operator %` is constrained with `treat_as_floating_point` type trait to limit the types to integral
+   representations only. Also `operator %(Rep)` takes `Rep` as a template argument to limit implicit
+   conversions.
+
 
 #### `quantity_cast`
 
diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index 3c5a803a..e9768e87 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -242,13 +242,16 @@ namespace units {
       return *this;
     }
 
-    constexpr quantity& operator%=(const rep& rhs)
+    template<Scalar Rep2>
+    constexpr quantity& operator%=(const Rep2& rhs)
+      requires (!treat_as_floating_point<rep> && !treat_as_floating_point<Rep2>)
     {
       value_ %= rhs;
       return *this;
     }
 
     constexpr quantity& operator%=(const quantity& q)
+        requires (!treat_as_floating_point<rep>)
     {
       value_ %= q.count();
       return *this;
diff --git a/test/unit_test/test_quantity.cpp b/test/unit_test/test_quantity.cpp
index 19c99b66..8d580c80 100644
--- a/test/unit_test/test_quantity.cpp
+++ b/test/unit_test/test_quantity.cpp
@@ -187,6 +187,13 @@ namespace {
   static_assert((2m /= 2).count() == 1);
   static_assert((7m %= 2).count() == 1);
   static_assert((7m %= 2m).count() == 1);
+//  static_assert((7.m %= 2.).count() == 1);  // should not compile
+//  static_assert((7.m %= 2).count() == 1);  // should not compile
+//  static_assert((7m %= 2.).count() == 1);  // should not compile
+  static_assert((7m %= 2m).count() == 1);
+//  static_assert((7.m %= 2.m).count() == 1);  // should not compile
+//  static_assert((7.m %= 2m).count() == 1);  // should not compile
+//  static_assert((7m %= 2.m).count() == 1);  // should not compile
 
   // non-member arithmetic operators