diff --git a/mupdf-64M-memory-limit.diff b/mupdf-64M-memory-limit.diff
new file mode 100644
index 000000000..94db74fd6
--- /dev/null
+++ b/mupdf-64M-memory-limit.diff
@@ -0,0 +1,12 @@
+diff --git a/fitz/res_pixmap.c b/fitz/res_pixmap.c
+index 83f4652..c4d7d6a 100644
+--- a/fitz/res_pixmap.c
++++ b/fitz/res_pixmap.c
+@@ -1,6 +1,6 @@
+ #include "fitz.h"
+ 
+-static int fz_memory_limit = 256 << 20;
++static int fz_memory_limit = 64 << 20; // XXX dpavlin - limit memory usage to 64M
+ static int fz_memory_used = 0;
+ 
+ fz_pixmap *
diff --git a/reader.lua b/reader.lua
index 9f24c53e7..872839cc5 100755
--- a/reader.lua
+++ b/reader.lua
@@ -117,7 +117,7 @@ function freecache()
 end
 function checkcache(no)
 	for i = 1, #cache do
-		if cache[i].no == no then
+		if cache[i].no == no and cache[i].page ~= nil then
 			print("cache hit: slot="..i.." page="..no)
 			return i
 		end
@@ -216,13 +216,12 @@ function modify_gamma(offset)
 	if gamma == -1 then
 		gamma = 1
 	end
-	print("modify_gamma slot="..slot.." gamma="..gamma.." offset="..offset)
+	local no = cache[slot].no
+	print("modify_gamma "..no.." slot="..slot.." gamma="..gamma.." offset="..offset)
 	gamma = gamma + offset;
-	cache[slot].dc:setGamma( gamma );
 	optarg["G"] = gamma; -- for next page
-	cache[slot].page:draw(cache[slot].dc, cache[slot].bb, 0, 0)
-	fb:blitFullFrom(cache[slot].bb)
-	fb:refresh(0)
+	freecache()
+	goto(no)
 end
 
 function mainloop()