diff --git a/ext/bcmath/bcmath.c b/ext/bcmath/bcmath.c
index f53032fabc35..bc78faa7b399 100644
--- a/ext/bcmath/bcmath.c
+++ b/ext/bcmath/bcmath.c
@@ -96,9 +96,9 @@ static PHP_GINIT_FUNCTION(bcmath)
 /* {{{ PHP_GSHUTDOWN_FUNCTION */
 static PHP_GSHUTDOWN_FUNCTION(bcmath)
 {
-	_bc_free_num_ex(&bcmath_globals->_zero_, 1);
-	_bc_free_num_ex(&bcmath_globals->_one_, 1);
-	_bc_free_num_ex(&bcmath_globals->_two_, 1);
+	bc_force_free_number(&bcmath_globals->_zero_);
+	bc_force_free_number(&bcmath_globals->_one_);
+	bc_force_free_number(&bcmath_globals->_two_);
 }
 /* }}} */
 
diff --git a/ext/bcmath/libbcmath/src/bcmath.h b/ext/bcmath/libbcmath/src/bcmath.h
index de51ee745711..0ec86f208619 100644
--- a/ext/bcmath/libbcmath/src/bcmath.h
+++ b/ext/bcmath/libbcmath/src/bcmath.h
@@ -87,6 +87,8 @@ typedef struct bc_struct {
 
 void bc_init_numbers(void);
 
+void bc_force_free_number(bc_num *num);
+
 bc_num _bc_new_num_ex(size_t length, size_t scale, bool persistent);
 
 void _bc_free_num_ex(bc_num *num, bool persistent);
diff --git a/ext/bcmath/libbcmath/src/init.c b/ext/bcmath/libbcmath/src/init.c
index cef55324689f..6bb538ef1cb1 100644
--- a/ext/bcmath/libbcmath/src/init.c
+++ b/ext/bcmath/libbcmath/src/init.c
@@ -82,6 +82,13 @@ void bc_init_numbers(void)
 	BCG(_two_)->n_value[0] = 2;
 }
 
+void bc_force_free_number(bc_num *num)
+{
+	pefree((*num)->n_ptr, 1);
+	pefree(*num, 1);
+	*num = NULL;
+}
+
 
 /* Make a copy of a number! Just increments the reference count! */
 bc_num bc_copy_num(bc_num num)
diff --git a/ext/bcmath/tests/gh17398.phpt b/ext/bcmath/tests/gh17398.phpt
new file mode 100644
index 000000000000..6a0cda09ec76
--- /dev/null
+++ b/ext/bcmath/tests/gh17398.phpt
@@ -0,0 +1,10 @@
+--TEST--
+GH-17398 (bcmul memory leak)
+--EXTENSIONS--
+bcmath
+--FILE--
+<?php
+bcmul('0', '0', 2147483647);
+?>
+--EXPECTF--
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %s on line %d