diff --git a/tools/imximage.c b/tools/imximage.c
index c1fdafbd7c..59923ffefa 100644
--- a/tools/imximage.c
+++ b/tools/imximage.c
@@ -25,6 +25,9 @@
  * MA 02111-1307 USA
  */
 
+/* Required to obtain the getline prototype from stdio.h */
+#define _GNU_SOURCE
+
 #include "mkimage.h"
 #include <image.h>
 #include "imximage.h"