diff --git a/ksysguardd/Linux/ProcessList.c b/ksysguardd/Linux/ProcessList.c
--- a/ksysguardd/Linux/ProcessList.c
+++ b/ksysguardd/Linux/ProcessList.c
@@ -643,26 +643,50 @@
 void setPriority( const char* cmd )
 {
   int pid, prio;
+  char task_dir[64];
+  DIR* task = 0;
+  struct dirent* thread;
+  int thread_id;
   /** as:  setpriority <pid> <priority> */
   sscanf( cmd, "%*s %d %d", &pid, &prio );
-  if ( setpriority( PRIO_PROCESS, pid, prio ) ) {
-    switch ( errno ) {
-      case EINVAL:
-        output( "4\t%d\t%d\n", pid, prio  );
-        break;
-      case ESRCH:
-        output( "3\t%d\t%d\nn", pid, prio );
-        break;
-      case EPERM:
-      case EACCES:
-        output( "2\t%d\t%d\n", pid, prio );
-        break;
-      default: /* unknown error */
-        output( "1\t%d\t%d\n", pid, prio );
-        break;
-    }
-  } else
+  if (snprintf( task_dir, sizeof(task_dir), "/proc/%d/task", pid) >= sizeof(task_dir))
+    goto failure;
+  task = opendir(task_dir);
+  if (!task)
+    goto failure;
+  /* NOTE: this is racy; threads may die or be spawned during our
+     iteration. Inthat case, we either fail with an error or fail to
+     set all threads' priorities */
+  while (errno = 0, thread = readdir(task)) {
+    if (thread->d_name[0] == '.')
+      continue;
+    if ( setpriority( PRIO_PROCESS, atoi(thread->d_name), prio ) )
+      goto failure;
+  }
+  if (!errno) {
+    closedir(task);
     output( "0\t%d\t%d\n",pid, prio );
+    return;
+  }
+
+ failure:
+  if (task) closedir(task);
+  switch ( errno ) {
+  case EINVAL:
+    output( "4\t%d\t%d\n", pid, prio  );
+    break;
+  case ESRCH:
+  case ENOENT:
+    output( "3\t%d\t%d\nn", pid, prio );
+    break;
+  case EPERM:
+  case EACCES:
+    output( "2\t%d\t%d\n", pid, prio );
+    break;
+  default: /* unknown error */
+    output( "1\t%d\t%d\n", pid, prio );
+    break;
+  }
 }
 
 void ioniceProcess( const char* cmd )