diff --git a/tests/lib/newlib/thread_safety/prj.conf b/tests/lib/newlib/thread_safety/prj.conf
index b797bc64b84..bce82d0d9a8 100644
--- a/tests/lib/newlib/thread_safety/prj.conf
+++ b/tests/lib/newlib/thread_safety/prj.conf
@@ -1,4 +1,5 @@
 CONFIG_ZTEST=y
 CONFIG_NEWLIB_LIBC=y
 CONFIG_NEWLIB_LIBC_NANO=n
+CONFIG_NEWLIB_LIBC_MIN_REQUIRED_HEAP_SIZE=0
 CONFIG_TIMESLICE_SIZE=1
diff --git a/tests/lib/newlib/thread_safety/prj_userspace.conf b/tests/lib/newlib/thread_safety/prj_userspace.conf
index 4e8eb900636..59a2c4f429f 100644
--- a/tests/lib/newlib/thread_safety/prj_userspace.conf
+++ b/tests/lib/newlib/thread_safety/prj_userspace.conf
@@ -1,6 +1,7 @@
 CONFIG_ZTEST=y
 CONFIG_NEWLIB_LIBC=y
 CONFIG_NEWLIB_LIBC_NANO=n
+CONFIG_NEWLIB_LIBC_MIN_REQUIRED_HEAP_SIZE=0
 CONFIG_TIMESLICE_SIZE=1
 
 CONFIG_TEST_USERSPACE=y