diff --git a/src/log.c b/src/log.c
index e0679e15..34e34532 100644
--- a/src/log.c
+++ b/src/log.c
@@ -129,10 +129,11 @@ void open_logbuffer(void) {
             return;
         }
 
-        if (ftruncate(logbuffer_shm, logbuffer_size) == -1) {
+        int ret;
+        if ((ret = posix_fallocate(logbuffer_shm, 0, logbuffer_size)) != 0) {
             close(logbuffer_shm);
             shm_unlink(shmlogname);
-            fprintf(stderr, "Could not ftruncate SHM segment for the i3 log: %s\n", strerror(errno));
+            fprintf(stderr, "Could not ftruncate SHM segment for the i3 log: %s\n", strerror(ret));
             return;
         }