diff --git a/boards/frdm-k22f/include/periph_conf.h b/boards/frdm-k22f/include/periph_conf.h
index 7e9ea7aa6e..a4f5908887 100644
--- a/boards/frdm-k22f/include/periph_conf.h
+++ b/boards/frdm-k22f/include/periph_conf.h
@@ -241,9 +241,9 @@ static const spi_conf_t spi_config[] = {
         .pin_cs   = {
             GPIO_PIN(PORT_C, 4),
             GPIO_PIN(PORT_D, 4),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI0_MASK
diff --git a/boards/frdm-k64f/include/periph_conf.h b/boards/frdm-k64f/include/periph_conf.h
index 3afa5c7e30..bc94d95423 100644
--- a/boards/frdm-k64f/include/periph_conf.h
+++ b/boards/frdm-k64f/include/periph_conf.h
@@ -237,10 +237,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_D, 1),
         .pin_cs   = {
             GPIO_PIN(PORT_D, 0),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI0_MASK
diff --git a/boards/frdm-kw41z/include/periph_conf.h b/boards/frdm-kw41z/include/periph_conf.h
index ed054ea0b6..2d1f26c32f 100644
--- a/boards/frdm-kw41z/include/periph_conf.h
+++ b/boards/frdm-kw41z/include/periph_conf.h
@@ -40,10 +40,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_C, 16),
         .pin_cs   = {
             GPIO_PIN(PORT_C, 19),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI0_MASK
@@ -55,10 +55,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_A, 18),
         .pin_cs   = {
             GPIO_PIN(PORT_A, 19),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI1_MASK
diff --git a/boards/mulle/include/periph_conf.h b/boards/mulle/include/periph_conf.h
index 303ddfd2c3..220ea1de7e 100644
--- a/boards/mulle/include/periph_conf.h
+++ b/boards/mulle/include/periph_conf.h
@@ -312,7 +312,7 @@ static const spi_conf_t spi_config[] = {
             GPIO_PIN(PORT_D, 4),
             GPIO_PIN(PORT_D, 5),
             GPIO_PIN(PORT_D, 6),
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI0_MASK
@@ -324,10 +324,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_E, 2),
         .pin_cs   = {
             GPIO_PIN(PORT_E, 4),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI1_MASK
diff --git a/boards/openlabs-kw41z-mini/include/periph_conf.h b/boards/openlabs-kw41z-mini/include/periph_conf.h
index 3278c172bf..80df305cff 100644
--- a/boards/openlabs-kw41z-mini/include/periph_conf.h
+++ b/boards/openlabs-kw41z-mini/include/periph_conf.h
@@ -315,10 +315,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_C, 16),
         .pin_cs   = {
             GPIO_PIN(PORT_C, 19),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
         },
         .pcr      = (gpio_pcr_t)(GPIO_AF_2 | GPIO_IN_PU),
         .simmask  = SIM_SCGC6_SPI0_MASK
diff --git a/boards/pba-d-01-kw2x/include/periph_conf.h b/boards/pba-d-01-kw2x/include/periph_conf.h
index 1466491b40..0bf510be48 100644
--- a/boards/pba-d-01-kw2x/include/periph_conf.h
+++ b/boards/pba-d-01-kw2x/include/periph_conf.h
@@ -223,10 +223,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_C, 5),
         .pin_cs   = {
             GPIO_PIN(PORT_C, 4),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI0_MASK
@@ -238,10 +238,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_B, 11),
         .pin_cs   = {
             GPIO_PIN(PORT_B, 10),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI1_MASK
diff --git a/boards/phynode-kw41z/include/periph_conf.h b/boards/phynode-kw41z/include/periph_conf.h
index 9b4cbb037d..808f0623a6 100644
--- a/boards/phynode-kw41z/include/periph_conf.h
+++ b/boards/phynode-kw41z/include/periph_conf.h
@@ -42,10 +42,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_A, 18),
         .pin_cs   = {
             GPIO_PIN(PORT_A, 19),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI1_MASK
diff --git a/boards/usb-kw41z/include/periph_conf.h b/boards/usb-kw41z/include/periph_conf.h
index c607b38394..46b09271e6 100644
--- a/boards/usb-kw41z/include/periph_conf.h
+++ b/boards/usb-kw41z/include/periph_conf.h
@@ -39,10 +39,10 @@ static const spi_conf_t spi_config[] = {
         .pin_clk  = GPIO_PIN(PORT_A, 18),
         .pin_cs   = {
             GPIO_PIN(PORT_A, 19),
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF,
-            GPIO_UNDEF
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
+            SPI_CS_UNDEF,
         },
         .pcr      = GPIO_AF_2,
         .simmask  = SIM_SCGC6_SPI1_MASK
diff --git a/cpu/kinetis/include/periph_cpu.h b/cpu/kinetis/include/periph_cpu.h
index 6cec6d6c23..5c17ab1824 100644
--- a/cpu/kinetis/include/periph_cpu.h
+++ b/cpu/kinetis/include/periph_cpu.h
@@ -115,6 +115,21 @@ typedef uint16_t gpio_t;
  */
 #define SPI_HWCS_NUMOF      (5)
 
+/**
+ * @brief   Define value for unused CS line
+ */
+#define SPI_CS_UNDEF        (GPIO_UNDEF)
+
+#ifndef DOXYGEN
+/**
+ * @brief   Overwrite the default spi_cs_t type definition
+ * @{
+ */
+#define HAVE_SPI_CS_T
+typedef uint32_t spi_cs_t;
+/** @} */
+#endif
+
 /**
  * @name    This CPU makes use of the following shared SPI functions
  * @{
@@ -454,7 +469,7 @@ typedef struct {
     gpio_t pin_miso;                    /**< MISO pin used */
     gpio_t pin_mosi;                    /**< MOSI pin used */
     gpio_t pin_clk;                     /**< CLK pin used */
-    gpio_t pin_cs[SPI_HWCS_NUMOF];      /**< pins used for HW cs lines */
+    spi_cs_t pin_cs[SPI_HWCS_NUMOF];    /**< pins used for HW cs lines */
 #ifdef KINETIS_HAVE_PCR
     gpio_pcr_t pcr;                     /**< alternate pin function values */
 #endif /* KINETIS_HAVE_PCR */
diff --git a/cpu/kinetis/periph/spi.c b/cpu/kinetis/periph/spi.c
index 52da320b2f..193277f01d 100644
--- a/cpu/kinetis/periph/spi.c
+++ b/cpu/kinetis/periph/spi.c
@@ -30,6 +30,7 @@
 
 #include "cpu.h"
 #include "mutex.h"
+#include "periph/gpio.h"
 #include "periph/spi.h"
 
 #define ENABLE_DEBUG        0
@@ -135,8 +136,7 @@ int spi_init_cs(spi_t bus, spi_cs_t cs)
         gpio_init((gpio_t)cs, GPIO_OUT);
     }
     else {
-        if ((cs >= SPI_HWCS_NUMOF) ||
-            (spi_config[bus].pin_cs[cs] == GPIO_UNDEF)) {
+        if ((cs >= SPI_HWCS_NUMOF) || !gpio_is_valid(spi_config[bus].pin_cs[cs])) {
             return SPI_NOCS;
         }
         gpio_init_port(spi_config[bus].pin_cs[cs], spi_config[bus].pcr);