diff --git a/map/multi_fixed.hpp b/map/multi_fixed.hpp
index 9393acfa..9208fce7 100644
--- a/map/multi_fixed.hpp
+++ b/map/multi_fixed.hpp
@@ -236,16 +236,29 @@ namespace cruft::map {
             m_store.data[m_size].~value_type ();
         }
 
+
+        /// Erases the keys pointed at by the supplied iterator range.
+        ///
+        /// If a key does not exist it is silently ignored.
+        ///
+        /// \return The number of keys erased.
         template <typename IteratorT>
-        void
+        std::size_t
         erase_keys (IteratorT first, IteratorT last)
         {
             CHECK (std::is_sorted (first, last));
 
+            std::size_t tally = 0;
+
             // HACK: This is hopelessly naive, but it works.
-            for (auto cursor = first; cursor != last; ++cursor)
-                if (auto pos = find (*cursor); pos != end ())
+            for (auto cursor = first; cursor != last; ++cursor) {
+                if (auto pos = find (*cursor); pos != end ()) {
                     erase (pos);
+                    ++tally;
+                }
+            }
+
+            return tally;
         }
 
 
diff --git a/test/map/multi_fixed.cpp b/test/map/multi_fixed.cpp
index 3f13bcc0..820ff2bf 100644
--- a/test/map/multi_fixed.cpp
+++ b/test/map/multi_fixed.cpp
@@ -90,9 +90,11 @@ int main ()
     {
         cruft::map::multi_fixed<4, int, int> init {{ {0,0}, {1,1}, {2,2}, {3,3} }};
         static constexpr int keys[] = { 1, 3 };
-        init.erase_keys (std::begin (keys), std::end (keys));
+        auto const count = init.erase_keys (std::begin (keys), std::end (keys));
+        tap.expect_eq (count, std::size (keys), "erase_keys count");
+
         cruft::map::multi_fixed<4, int, int> expected {{ {0,0}, {2,2} }};
-        tap.expect_eq (init, expected, "erase_keys");
+        tap.expect_eq (init, expected, "erase_keys values");
     }