diff --git a/include/mbedtls/threading.h b/include/mbedtls/threading.h
index 2ec41a4..6830bb4 100644
--- a/include/mbedtls/threading.h
+++ b/include/mbedtls/threading.h
@@ -25,7 +25,7 @@
 #define MBEDTLS_THREADING_H
 
 /*
- * Ensure gmtime_r is available even with -std=c99; must be included before
+ * Ensure gmtime_r is available even with -std=c99; must be defined before
  * config.h, which pulls in glibc's features.h. Harmless on other platforms.
  */
 #if !defined(_POSIX_C_SOURCE)