diff --git a/cmake/spdlog_config.h.in b/cmake/spdlog_config.h.in
index 1148ed92..6c2fe3b4 100644
--- a/cmake/spdlog_config.h.in
+++ b/cmake/spdlog_config.h.in
@@ -28,4 +28,5 @@
 // Use external fmtlib instead of bundled
 #cmakedefine SPDLOG_FMT_EXTERNAL
 
+// Whether fwrite_unlocked is available
 #cmakedefine SPDLOG_FWRITE_UNLOCKED