diff --git a/apps/deluge/deluge.c b/apps/deluge/deluge.c
index e989a2ebe..9e3235b25 100644
--- a/apps/deluge/deluge.c
+++ b/apps/deluge/deluge.c
@@ -633,7 +633,7 @@ deluge_disseminate(char *file, unsigned version)
   if(next_object_id > 0 || init_object(&current_object, file, version) < 0) {
     return -1;
   }
-  process_start(&deluge_process, file);
+  process_start(&deluge_process, (void *)file);
 
   return 0;
 }
diff --git a/apps/http-post-auth/http-post-auth.c b/apps/http-post-auth/http-post-auth.c
index 71c493836..4bf0cdeae 100644
--- a/apps/http-post-auth/http-post-auth.c
+++ b/apps/http-post-auth/http-post-auth.c
@@ -162,7 +162,7 @@ http_post_auth(const uint8_t *username_password, const char *msg)
       PRINTF("message '%s'\n", s->message);*/
 
   /* Spawn process to deal with TCP connection */
-  process_start(&http_post_auth_process, (char *)s);
+  process_start(&http_post_auth_process, (void *)s);
   return 1;
 }
 /*---------------------------------------------------------------------------*/
diff --git a/apps/shell/shell-rime-netcmd.c b/apps/shell/shell-rime-netcmd.c
index 08acc2ed1..cadcd993a 100644
--- a/apps/shell/shell-rime-netcmd.c
+++ b/apps/shell/shell-rime-netcmd.c
@@ -159,7 +159,7 @@ recv_trickle(struct trickle_conn *c)
     
     if(crc == crc16_data(msg->netcmd, len, 0)) {
       /* Start the server process with the incoming command. */
-      process_start(&shell_netcmd_server_process, msg->netcmd);
+      process_start(&shell_netcmd_server_process, (void *)msg->netcmd);
     }
   }
 }
diff --git a/apps/shell/shell-rime-sendcmd.c b/apps/shell/shell-rime-sendcmd.c
index ac173c2a8..b3179c54b 100644
--- a/apps/shell/shell-rime-sendcmd.c
+++ b/apps/shell/shell-rime-sendcmd.c
@@ -162,7 +162,7 @@ recv_uc(struct unicast_conn *c, const linkaddr_t *from)
 
     if(crc == crc16_data(msg->sendcmd, len, 0)) {
       /* Start the server process with the incoming command. */
-      process_start(&shell_sendcmd_server_process, msg->sendcmd);
+      process_start(&shell_sendcmd_server_process, (void *)msg->sendcmd);
     }
   }
 }
diff --git a/apps/shell/shell-time.c b/apps/shell/shell-time.c
index eb7ceec7c..0c3ac03c1 100644
--- a/apps/shell/shell-time.c
+++ b/apps/shell/shell-time.c
@@ -266,7 +266,7 @@ PROCESS_THREAD(shell_repeat_process, ev, data)
   etimer_set(&etimer, CLOCK_SECOND * period);
   for(i = 0; reps == 0 || i < reps; ++i) {
 
-    process_start(&shell_repeat_server_process, command);
+    process_start(&shell_repeat_server_process, (void *)command);
     process_post(&shell_repeat_server_process,
 		 PROCESS_EVENT_CONTINUE,
 		 &shell_repeat_process);
diff --git a/apps/shell/shell.c b/apps/shell/shell.c
index fd909c791..4f4d74efa 100644
--- a/apps/shell/shell.c
+++ b/apps/shell/shell.c
@@ -298,7 +298,7 @@ start_command(char *commandline, struct shell_command *child)
     c->child = child;
     /*    printf("shell: start_command starting '%s'\n", c->process->name);*/
     /* Start a new process for the command. */
-    process_start(c->process, args);
+    process_start(c->process, (void *)args);
   }
   
   return c;
@@ -364,7 +364,7 @@ shell_input(char *commandline, int commandline_len)
 
   if(commandline[0] == '~' &&
      commandline[1] == 'K') {
-    /*    process_start(&shell_killall_process, commandline);*/
+    /*    process_start(&shell_killall_process, (void *)commandline);*/
     if(front_process != &shell_process) {
       process_exit(front_process);
     }
diff --git a/core/loader/dlloader.c b/core/loader/dlloader.c
index 88987bbfb..7d3e8320e 100644
--- a/core/loader/dlloader.c
+++ b/core/loader/dlloader.c
@@ -62,7 +62,7 @@ dlloader_load(char *path, char *arg)
   /* Start the process. */
  
   printf("Starting '%s'\n", PROCESS_NAME_STRING(*p));
-  process_start(*p, arg);
+  process_start(*p, (void *)arg);
 
   return LOADER_OK;
 }
diff --git a/core/sys/process.c b/core/sys/process.c
index 8a7496d75..ef28f80f4 100644
--- a/core/sys/process.c
+++ b/core/sys/process.c
@@ -96,7 +96,7 @@ process_alloc_event(void)
 }
 /*---------------------------------------------------------------------------*/
 void
-process_start(struct process *p, const char *arg)
+process_start(struct process *p, process_data_t data)
 {
   struct process *q;
 
@@ -117,7 +117,7 @@ process_start(struct process *p, const char *arg)
   PRINTF("process: starting '%s'\n", PROCESS_NAME_STRING(p));
 
   /* Post a synchronous initialization event to the process. */
-  process_post_synch(p, PROCESS_EVENT_INIT, (process_data_t)arg);
+  process_post_synch(p, PROCESS_EVENT_INIT, data);
 }
 /*---------------------------------------------------------------------------*/
 static void
diff --git a/core/sys/process.h b/core/sys/process.h
index 7063ee024..43547f3bd 100644
--- a/core/sys/process.h
+++ b/core/sys/process.h
@@ -339,7 +339,7 @@ struct process {
  * process
  *
  */
-CCIF void process_start(struct process *p, const char *arg);
+CCIF void process_start(struct process *p, process_data_t data);
 
 /**
  * Post an asynchronous event.
@@ -362,7 +362,7 @@ CCIF void process_start(struct process *p, const char *arg);
  * \retval PROCESS_ERR_FULL The event queue was full and the event could
  * not be posted.
  */
-CCIF int process_post(struct process *p, process_event_t ev, void* data);
+CCIF int process_post(struct process *p, process_event_t ev, process_data_t data);
 
 /**
  * Post a synchronous event to a process.
@@ -375,7 +375,7 @@ CCIF int process_post(struct process *p, process_event_t ev, void* data);
  * with the event.
  */
 CCIF void process_post_synch(struct process *p,
-			     process_event_t ev, void* data);
+			     process_event_t ev, process_data_t data);
 
 /**
  * \brief      Cause a process to exit
diff --git a/platform/apple2enh/contiki-main.c b/platform/apple2enh/contiki-main.c
index 2637da92e..0d0751c1a 100644
--- a/platform/apple2enh/contiki-main.c
+++ b/platform/apple2enh/contiki-main.c
@@ -112,7 +112,7 @@ main(void)
 
   procinit_init();
 
-  process_start((struct process *)&ethernet_process, (char *)ethernet_config);
+  process_start((struct process *)&ethernet_process, (void *)ethernet_config);
 
   autostart_start(autostart_processes);
 
diff --git a/platform/atarixl/contiki-main.c b/platform/atarixl/contiki-main.c
index 268cd10ba..61cd4c7bb 100644
--- a/platform/atarixl/contiki-main.c
+++ b/platform/atarixl/contiki-main.c
@@ -108,7 +108,7 @@ main(void)
 
   procinit_init();
 
-  process_start((struct process *)&ethernet_process, (char *)ethernet_config);
+  process_start((struct process *)&ethernet_process, (void *)ethernet_config);
 
   autostart_start(autostart_processes);
 
diff --git a/platform/c128/contiki-main.c b/platform/c128/contiki-main.c
index 128ccb9f1..c3d15f478 100644
--- a/platform/c128/contiki-main.c
+++ b/platform/c128/contiki-main.c
@@ -126,7 +126,7 @@ main(void)
 
   procinit_init();
 
-  process_start((struct process *)&ethernet_process, (char *)ethernet_config);
+  process_start((struct process *)&ethernet_process, (void *)ethernet_config);
 
   autostart_start(autostart_processes);
 
diff --git a/platform/c64/contiki-main.c b/platform/c64/contiki-main.c
index e6ebfdb3a..57a333f0b 100644
--- a/platform/c64/contiki-main.c
+++ b/platform/c64/contiki-main.c
@@ -124,7 +124,7 @@ main(void)
 
   procinit_init();
 
-  process_start((struct process *)&ethernet_process, (char *)ethernet_config);
+  process_start((struct process *)&ethernet_process, (void *)ethernet_config);
 
   autostart_start(autostart_processes);
 
diff --git a/platform/win32/loader/dll-loader.c b/platform/win32/loader/dll-loader.c
index eb252947e..4a2393425 100644
--- a/platform/win32/loader/dll-loader.c
+++ b/platform/win32/loader/dll-loader.c
@@ -62,7 +62,7 @@ dll_loader_load(char *name, char *arg)
 
   /* Start the process. */
   debug_printf("Starting '%s'\n", (**(struct process ***)&p)->name);
-  process_start(**(struct process ***)&p, arg);
+  process_start(**(struct process ***)&p, (void *)arg);
 
   return LOADER_OK;
 }