diff --git a/codecs/gsm/Makefile b/codecs/gsm/Makefile
index 8bc53e88d5..9058f1293c 100644
--- a/codecs/gsm/Makefile
+++ b/codecs/gsm/Makefile
@@ -242,7 +242,7 @@ ifneq ($(shell uname -m),armv4l)
 ifneq ($(shell uname -m),sparc64)
 ifneq (${PROC},arm)
 ifneq ($(shell uname -m), parisc)
-ifneq ($(shell uname -m), s390)
+ifneq (${PROC}, s390)
 GSM_SOURCES+= $(SRC)/k6opt.s
 endif
 endif