diff --git a/include/shmlog.h b/include/shmlog.h
index fd3f53eb..94da2bdb 100644
--- a/include/shmlog.h
+++ b/include/shmlog.h
@@ -14,6 +14,9 @@
 #include <stdint.h>
 #include <pthread.h>
 
+/* Default shmlog size if not set by user. */
+extern const int default_shmlog_size;
+
 /*
  * Header of the shmlog file. Used by i3/src/log.c and i3/i3-dump-log/main.c.
  *
diff --git a/src/main.c b/src/main.c
index db3aca49..0912d48e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -19,6 +19,7 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include "all.h"
+#include "shmlog.h"
 
 #include "sd-daemon.h"
 
@@ -67,6 +68,9 @@ xcb_key_symbols_t *keysyms;
 /* Those are our connections to X11 for use with libXcursor and XKB */
 Display *xlibdpy, *xkbdpy;
 
+/* Default shmlog size if not set by user. */
+const int default_shmlog_size = 25 * 1024 * 1024;
+
 /* The list of key bindings */
 struct bindings_head *bindings;
 
@@ -291,7 +295,7 @@ int main(int argc, char *argv[]) {
     init_logging();
 
     /* On non-release builds, disable SHM logging by default. */
-    shmlog_size = (is_debug_build() ? 25 * 1024 * 1024 : 0);
+    shmlog_size = (is_debug_build() ? default_shmlog_size : 0);
 
     start_argv = argv;