diff --git a/Makefile b/Makefile
index 921a71f3..bd50490c 100755
--- a/Makefile
+++ b/Makefile
@@ -42,16 +42,14 @@ ifeq ($(shell echo $(ARCHES) | sed 's/.*source.*/1/'),1)
 	export INC_SOURCE=yes
 endif
 
-export NUM_ARCHES=$(shell echo $(ARCHES) | wc -w)
-ifeq ($(NUM_ARCHES),1)
-    ARCH_MKISOFS = ${${ARCHES}_MKISOFS}
-    ARCH_MKISOFS_OPTS = ${${ARCHES}_MKISOFS_OPTS}
-    ifneq (${ARCH_MKISOFS},)
-        MKISOFS = ${ARCH_MKISOFS}
-    endif
-    ifneq (${ARCH_MKISOFS_OPTS},)
-        MKISOFS_OPTS = ${ARCH_MKISOFS_OPTS}
-    endif
+UNDER_ARCHES=$(shell echo $(ARCHES) | sed 's/\ /_/g')
+ARCH_MKISOFS = ${${UNDER_ARCHES}_MKISOFS}
+ARCH_MKISOFS_OPTS = ${${UNDER_ARCHES}_MKISOFS_OPTS}
+ifneq (${ARCH_MKISOFS},)
+    MKISOFS = ${ARCH_MKISOFS}
+endif
+ifneq (${ARCH_MKISOFS_OPTS},)
+    MKISOFS_OPTS = ${ARCH_MKISOFS_OPTS}
 endif
 
 ## Internal variables