diff --git a/src/runtime/malloc.h b/src/runtime/malloc.h
index d1d9e95e98f..530dfc98f1f 100644
--- a/src/runtime/malloc.h
+++ b/src/runtime/malloc.h
@@ -91,7 +91,7 @@ typedef	uintptr	PageID;		// address >> PageShift
 enum
 {
 	// Tunable constants.
-	NumSizeClasses = 150,		// Number of size classes (must match msize.c)
+	NumSizeClasses = 67,		// Number of size classes (must match msize.c)
 	MaxSmallSize = 32<<10,
 
 	FixAllocChunk = 128<<10,	// Chunk size for FixAlloc
diff --git a/src/runtime/msize.c b/src/runtime/msize.c
index 62d5c3ad99b..25e22637d28 100644
--- a/src/runtime/msize.c
+++ b/src/runtime/msize.c
@@ -82,7 +82,7 @@ InitSizes(void)
 		// so wasted space is at most 12.5%.
 		allocsize = PageSize;
 		osize = size + RefcountOverhead;
-		while(allocsize%osize > (PageSize/8))
+		while(allocsize%osize > (allocsize/8))
 			allocsize += PageSize;
 		npages = allocsize >> PageShift;