diff --git a/libbb/compare_string_array.c b/libbb/compare_string_array.c
index 993b462..8961e00 100644
--- a/libbb/compare_string_array.c
+++ b/libbb/compare_string_array.c
@@ -17,7 +17,8 @@
 #include <string.h>
 
 /* returns the array number of the string */
-extern unsigned short compare_string_array(const char *string_array[], const char *key)
+extern unsigned short 
+compare_string_array(const char * const string_array[], const char *key)
 {
 	unsigned short i;