diff --git a/MagickCore/quantize.c b/MagickCore/quantize.c
index cadabd9..84eee6a 100644
--- a/MagickCore/quantize.c
+++ b/MagickCore/quantize.c
@@ -1434,7 +1434,7 @@
   size_t
     number_threads;
 
-  number_threads=GetMagickResourceLimit(ThreadResource);
+  number_threads=(size_t) GetMagickResourceLimit(ThreadResource);
   pixels=(RealPixelInfo **) AcquireQuantumMemory(number_threads,
     sizeof(*pixels));
   if (pixels == (RealPixelInfo **) NULL)