--- pngcrush-1.6.2/Makefile
+++ pngcrush-1.6.2/Makefile
@@ -10,7 +10,7 @@
 
 # macros --------------------------------------------------------------------
 
-GAS_VERSION := $(shell as --version | grep "GNU assembler" | sed -e 's/GNU assembler //' -e 's/ .*//')
+GAS_VERSION := $(shell as --version < /dev/null 2&>1 | grep "GNU assembler" | sed -e 's/GNU assembler //' -e 's/ .*//')
 
 # uncomment these 2 lines only if you are using an external copy of zlib:
 #ZINC = ../../zlib