diff --git a/library/gcm.c b/library/gcm.c
index 39cb189..522a8b1 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -136,7 +136,7 @@
         ctx->HH[i] = vh;
     }
 
-    for( i = 2; i < 16; i <<= 1 )
+    for( i = 2; i <= 8; i *= 2 )
     {
         uint64_t *HiL = ctx->HL + i, *HiH = ctx->HH + i;
         vh = *HiH;