diff --git a/sys/src/9/pc64/mmu.c b/sys/src/9/pc64/mmu.c
index db00fee37..af7b0eebb 100644
--- a/sys/src/9/pc64/mmu.c
+++ b/sys/src/9/pc64/mmu.c
@@ -347,7 +347,7 @@ mmuzap(void)
 			if(w & 1)
 				pte[x] = 0;
 			x++;
-			x >>= 1;
+			w >>= 1;
 		} while(w);
 		m->mmumap[i] = 0;
 	}