diff --git a/samples/net/coaps_client/src/coaps_client.c b/samples/net/coaps_client/src/coaps_client.c
index 3f76d1bf075..c2ffa54f735 100644
--- a/samples/net/coaps_client/src/coaps_client.c
+++ b/samples/net/coaps_client/src/coaps_client.c
@@ -411,7 +411,7 @@ exit:
 }
 
 #define STACK_SIZE		4096
-u8_t stack[STACK_SIZE];
+K_THREAD_STACK_DEFINE(stack, STACK_SIZE);
 static struct k_thread thread_data;
 
 static inline int init_app(void)
diff --git a/samples/net/coaps_server/src/coaps_server.c b/samples/net/coaps_server/src/coaps_server.c
index 2797c8a6c9f..92563b143f0 100644
--- a/samples/net/coaps_server/src/coaps_server.c
+++ b/samples/net/coaps_server/src/coaps_server.c
@@ -632,7 +632,7 @@ exit:
 }
 
 #define STACK_SIZE		4096
-u8_t stack[STACK_SIZE];
+K_THREAD_STACK_DEFINE(stack, STACK_SIZE);
 static struct k_thread thread_data;
 
 static inline int init_app(void)
diff --git a/samples/net/mbedtls_dtlsclient/src/dtls_client.c b/samples/net/mbedtls_dtlsclient/src/dtls_client.c
index aa81712680d..3a50647c81f 100644
--- a/samples/net/mbedtls_dtlsclient/src/dtls_client.c
+++ b/samples/net/mbedtls_dtlsclient/src/dtls_client.c
@@ -284,7 +284,7 @@ exit:
 }
 
 #define STACK_SIZE		8192
-u8_t stack[STACK_SIZE];
+K_THREAD_STACK_DEFINE(stack, STACK_SIZE);
 static struct k_thread dtls_thread;
 
 static inline int init_app(void)
diff --git a/samples/net/mbedtls_dtlsserver/src/dtls_server.c b/samples/net/mbedtls_dtlsserver/src/dtls_server.c
index 4e865430407..2383728cbf4 100644
--- a/samples/net/mbedtls_dtlsserver/src/dtls_server.c
+++ b/samples/net/mbedtls_dtlsserver/src/dtls_server.c
@@ -362,7 +362,7 @@ exit:
 }
 
 #define STACK_SIZE		8192
-u8_t stack[STACK_SIZE];
+K_THREAD_STACK_DEFINE(stack, STACK_SIZE);
 static struct k_thread dtls_thread;
 
 static inline int init_app(void)
diff --git a/samples/net/mbedtls_sslclient/src/mini_client.c b/samples/net/mbedtls_sslclient/src/mini_client.c
index 5c64aab773f..71c3f355898 100644
--- a/samples/net/mbedtls_sslclient/src/mini_client.c
+++ b/samples/net/mbedtls_sslclient/src/mini_client.c
@@ -315,7 +315,7 @@ exit:
 }
 
 #define STACK_SIZE		8192
-u8_t stack[STACK_SIZE];
+K_THREAD_STACK_DEFINE(stack, STACK_SIZE);
 static struct k_thread tls_thread;
 
 void main(void)