diff --git a/bench/Makefile b/bench/Makefile
index a2afeda7..e96429da 100644
--- a/bench/Makefile
+++ b/bench/Makefile
@@ -39,6 +39,7 @@ bench-mlib:
 	@./bench-mlib.exe 42
 	@./bench-mlib.exe 43
 	@./bench-mlib.exe 50
+	@./bench-mlib.exe 51
 
 bench-mlib-mempool:
 	$(CC) $(CFLAGS) $(CPPFLAGS) bench-mlib.c -DUSE_MEMPOOL -pthread -o bench-mlib-mempool.exe
@@ -50,6 +51,7 @@ bench-mlib-mempool:
 	@./bench-mlib-mempool.exe 42
 	@./bench-mlib-mempool.exe 43
 	@./bench-mlib-mempool.exe 50
+	@./bench-mlib-mempool.exe 51
 
 bench-mlib-thread:
 	$(CC) $(CFLAGS) $(CPPFLAGS) bench-mlib.c -DMULTI_THREAD_MEASURE -pthread -o bench-mlib-thread.exe
@@ -66,6 +68,7 @@ bench-stl:
 	@./bench-stl.exe 42
 	@./bench-stl.exe 43
 	@./bench-stl.exe 50
+	@./bench-stl.exe 51
 
 # QT is supposed to be installed
 bench-qt:
diff --git a/bench/bench-mlib.c b/bench/bench-mlib.c
index 8a607c09..2a71bee4 100644
--- a/bench/bench-mlib.c
+++ b/bench/bench-mlib.c
@@ -263,6 +263,17 @@ static void test_sort(size_t n)
   }
 }
 
+static void test_stable_sort(size_t n)
+{
+  M_LET(a1, ARRAY_OPLIST(array_float)) {
+    for(size_t i = 0; i < n; i++) {
+      array_float_push_back(a1, rand_get() );
+    }
+    array_float_special_stable_sort(a1);
+    g_result = *array_float_get(a1, 0);
+  }
+}
+
 /********************************************************************************************/
 
 BUFFER_DEF(buffer_uint, unsigned int, 0, BUFFER_QUEUE|BUFFER_BLOCKING)
@@ -485,6 +496,8 @@ int main(int argc, const char *argv[])
     test_function("DictS  time", 1000000, test_dict_str);
   if (n == 50)
     test_function("Sort   time", 10000000, test_sort);
+  if (n == 51)
+    test_function("Stable Sort time", 10000000, test_stable_sort);
   if (n == 60)
     test_function("Buffer time", 1000000, test_buffer);
   if (n == 61)
diff --git a/bench/bench-stl.cpp b/bench/bench-stl.cpp
index a34c7d09..ad9a0de6 100644
--- a/bench/bench-stl.cpp
+++ b/bench/bench-stl.cpp
@@ -208,6 +208,16 @@ static void test_sort(size_t n)
   g_result = a1[0];
 }
 
+static void test_stable_sort(size_t n)
+{
+  vector<float> a1;
+  for(size_t i = 0; i < n; i++) {
+    a1.push_back(rand_get() );
+  }
+  stable_sort(a1.begin(), a1.end());
+  g_result = a1[0];
+}
+
 /********************************************************************************************/
 
 int main(int argc, const char *argv[])
@@ -231,5 +241,7 @@ int main(int argc, const char *argv[])
     test_function("DictS(m)  time", 1000000, test_dict_str2);
   if (n == 50)
     test_function("Sort   time", 10000000, test_sort);
+  if (n == 51)
+    test_function("Stable Sort time", 10000000, test_stable_sort);
   exit(0);
 }