diff --git a/mfapi/patch.c b/mfapi/patch.c
index a96dcf4..92ffbe6 100644
--- a/mfapi/patch.c
+++ b/mfapi/patch.c
@@ -17,7 +17,7 @@
  */
 
 #define _POSIX_C_SOURCE 200809L // for strdup
-#defein _BSD_SOURCE             // for strdup on old systems
+#define _BSD_SOURCE             // for strdup on old systems
 
 #include <stdint.h>
 #include <openssl/sha.h>