diff --git a/ext/date/zonetab.h b/ext/date/zonetab.h
index 90eee4dc29..2a2e8910c9 100644
--- a/ext/date/zonetab.h
+++ b/ext/date/zonetab.h
@@ -51,7 +51,7 @@ struct zone;
 
 #ifndef GPERF_DOWNCASE
 #define GPERF_DOWNCASE 1
-static const unsigned char gperf_downcase[256] =
+static unsigned char gperf_downcase[256] =
   {
       0,   1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,  14,
      15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29,