diff --git a/src/peigs/DEFS b/src/peigs/DEFS
index 4eda9790f6..93f0fedc8d 100644
--- a/src/peigs/DEFS
+++ b/src/peigs/DEFS
@@ -470,7 +470,7 @@ endif
 
 ifeq ($(peigs_TARGET),$(findstring $(peigs_TARGET),LINUX64 CYGWIN64 CATAMOUNT))
 #alpha with /tcgmsg
-_CPU = $(shell uname -m  )
+_CPU := $(shell uname -m  )
 #hack for mingw64
 ifeq ($(_CPU),amd64)
 _CPU = x86_64