diff --git a/configure.in b/configure.in
index 3e936ae422f..174c9a16d8e 100644
--- a/configure.in
+++ b/configure.in
@@ -805,6 +805,9 @@ AC_SUBST(WRAPLIBS)
 if test "$TARGET_LINUX" = "true"; then
   AC_MSG_CHECKING([for atomic operations])
 
+  AC_LANG_SAVE
+  AC_LANG_CPLUSPLUS
+
   atom_ops=
   AC_TRY_RUN([
 #include <asm/atomic.h>
@@ -840,6 +843,8 @@ int main()
   if test -z "$atom_ops"; then atom_ops="no"; fi
   AC_MSG_RESULT($atom_ops)
 
+  AC_LANG_RESTORE
+
   AC_ARG_WITH(pstack,
     [  --with-pstack           Use the pstack backtrace library],
     [ USE_PSTACK=$withval ],
diff --git a/mysql-test/r/func_op.result b/mysql-test/r/func_op.result
index 61b29e9380d..24685d07f3d 100644
--- a/mysql-test/r/func_op.result
+++ b/mysql-test/r/func_op.result
@@ -35,3 +35,14 @@ select -1 >> 0, -1 << 0;
 select -1 >> 1, -1 << 1;
 -1 >> 1	-1 << 1
 9223372036854775807	18446744073709551614
+drop table if exists t1,t2;
+create table t1(a int);
+create table t2(a int, b int);
+insert into t1 values (1), (2), (3);
+insert into t2 values (1, 7), (3, 7);
+select t1.a, t2.a, t2.b, bit_count(t2.b) from t1 left join t2 on t1.a=t2.a;
+a	a	b	bit_count(t2.b)
+1	1	7	3
+2	NULL	NULL	NULL
+3	3	7	3
+drop table t1, t2;
diff --git a/mysql-test/t/func_op.test b/mysql-test/t/func_op.test
index 24266150e4c..0a4f5034f4c 100644
--- a/mysql-test/t/func_op.test
+++ b/mysql-test/t/func_op.test
@@ -17,4 +17,18 @@ select  0 | -1,  0 ^ -1,  0 & -1;
 select -1 >> 0, -1 << 0;
 select -1 >> 1, -1 << 1;
 
+#
+# Bug 13044: wrong bit_count() results
+#
+
+--disable_warnings
+drop table if exists t1,t2;
+--enable_warnings
+create table t1(a int);
+create table t2(a int, b int);
+insert into t1 values (1), (2), (3);
+insert into t2 values (1, 7), (3, 7);
+select t1.a, t2.a, t2.b, bit_count(t2.b) from t1 left join t2 on t1.a=t2.a;
+drop table t1, t2;
+
 # End of 4.1 tests
diff --git a/sql/item_func.cc b/sql/item_func.cc
index f40f868f75f..e22a7b45f33 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -2462,11 +2462,8 @@ longlong Item_func_bit_count::val_int()
 {
   DBUG_ASSERT(fixed == 1);
   ulonglong value= (ulonglong) args[0]->val_int();
-  if (args[0]->null_value)
-  {
-    null_value=1; /* purecov: inspected */
+  if ((null_value= args[0]->null_value))
     return 0; /* purecov: inspected */
-  }
   return (longlong) my_count_bits(value);
 }