diff --git a/mfapi/apicalls/upload_patch.c b/mfapi/apicalls/upload_patch.c
index ce17cfa..3248a13 100644
--- a/mfapi/apicalls/upload_patch.c
+++ b/mfapi/apicalls/upload_patch.c
@@ -18,6 +18,7 @@
  */
 
 #define _POSIX_C_SOURCE 200809L // for strdup
+#define _BSD_SOURCE				// for strdup on old systems
 
 #include <jansson.h>
 #include <stdlib.h>
diff --git a/mfapi/apicalls/upload_simple.c b/mfapi/apicalls/upload_simple.c
index feb4404..5cddf38 100644
--- a/mfapi/apicalls/upload_simple.c
+++ b/mfapi/apicalls/upload_simple.c
@@ -18,6 +18,7 @@
  */
 
 #define _POSIX_C_SOURCE 200809L // for strdup
+#define _BSD_SOURCE				// for strdup on old systems
 
 #include <jansson.h>
 #include <stdlib.h>
diff --git a/mfapi/apicalls/user_get_session_token.c b/mfapi/apicalls/user_get_session_token.c
index 0326457..65df3b2 100644
--- a/mfapi/apicalls/user_get_session_token.c
+++ b/mfapi/apicalls/user_get_session_token.c
@@ -18,6 +18,7 @@
  */
 
 #define _POSIX_C_SOURCE 200809L // for strdup
+#define _BSD_SOURCE             // for strdup on old systems
 
 #include <jansson.h>
 #include <stdint.h>