=== modified file 'build'
--- build	2017-11-15 00:36:27 +0000
+++ build	2017-11-15 00:33:54 +0000
@@ -12,7 +12,7 @@
 
 name=$1
 shift
-target=$(base64 -w 0 <<<${(j::)${(oq)@}} | tr /+ _-).$name \
+target=$(base64 -w 0 <<<${(j::)${(oq)@}} | tr +/ -_).$name \
 	|| die "Failed to generate target name"
 target=${(j::)${(oq)@}}.$name
 mkdir -p meta || exit $?

=== modified file 'common.zsh'
--- common.zsh	2017-11-15 00:36:27 +0000
+++ common.zsh	2017-11-15 00:33:54 +0000
@@ -27,7 +27,7 @@
 decode_args() {
 	typeset -gA vars
 	local arg decoded
-	decoded=$(tr <<<${BASE##*/} _- /+ | base64 -d)
+	decoded=$(tr <<<${BASE##*/} -_ +/ | base64 -d)
 	for arg in "${(s::Q)decoded}"; do
 		if [[ "$arg" != *=* ]]; then
 			echo >&2 "Malformed argument: ${(qqq)arg}"
@@ -119,7 +119,7 @@
 	else
 		run=( redo-ifchange )
 	fi
-	target=$(base64 -w 0 <<<${(j::)${(oq)new_vars}} | tr /+ _-).$name \
+	target=$(base64 -w 0 <<<${(j::)${(oq)new_vars}} | tr +/ -_).$name \
 		|| die "Failed to generate target name"
 	"$run[@]" meta/$target || die "Building $name failed ($target)"