diff --git a/cpu/msp430/dev/uart0-putchar.c b/cpu/msp430/dev/uart0-putchar.c
index c9fa974a6..e797e8b28 100644
--- a/cpu/msp430/dev/uart0-putchar.c
+++ b/cpu/msp430/dev/uart0-putchar.c
@@ -1,7 +1,7 @@
 #include <stdio.h>
 #include "dev/uart0.h"
 
-#ifndef NETSTACK_CONF_WITH_IPV4
+#if !NETSTACK_CONF_WITH_IPV4
 /* In case of IPv4: putchar() is defined by the SLIP driver */
 int
 putchar(int c)
@@ -9,4 +9,4 @@ putchar(int c)
   uart0_writeb((char)c);
   return c;
 }
-#endif /* NETSTACK_CONF_WITH_IPV4 */
+#endif /* ! NETSTACK_CONF_WITH_IPV4 */
diff --git a/cpu/msp430/dev/uart1-putchar.c b/cpu/msp430/dev/uart1-putchar.c
index c966b920d..e005ff255 100644
--- a/cpu/msp430/dev/uart1-putchar.c
+++ b/cpu/msp430/dev/uart1-putchar.c
@@ -1,7 +1,7 @@
 #include <stdio.h>
 #include "dev/uart1.h"
 
-#ifndef NETSTACK_CONF_WITH_IPV4
+#if !NETSTACK_CONF_WITH_IPV4
 /* In case of IPv4: putchar() is defined by the SLIP driver */
 int
 putchar(int c)
@@ -9,4 +9,4 @@ putchar(int c)
   uart1_writeb((char)c);
   return c;
 }
-#endif /* NETSTACK_CONF_WITH_IPV4 */
+#endif /* ! NETSTACK_CONF_WITH_IPV4 */