diff --git a/src/Makefile b/src/Makefile
index 30e8fd5..66167fe 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -106,30 +106,30 @@ JSSRC=					\
 	node/TimeEdit.js		\
 	node/TimeView.js
 
-all: ${SUBDIRS}
-	set -e && for i in ${SUBDIRS}; do ${MAKE} -C $$i; done
+all: $(SUBDIRS)
+	set -e && for i in $(SUBDIRS); do $(MAKE) -C $$i; done
 
-.lint-incremental: ${JSSRC}
+.lint-incremental: $(JSSRC)
 	eslint $?
 	touch "$@"
 
 .PHONY: lint
 check: lint
 	eslint --strict api-viewer/APIViewer.js
-lint: ${JSSRC}
-	eslint --strict ${JSSRC}
+lint: $(JSSRC)
+	eslint --strict $(JSSRC)
 	touch ".lint-incremental"
 
-proxmoxlib.js: .lint-incremental ${JSSRC}
+proxmoxlib.js: .lint-incremental $(JSSRC)
 	# add the version as comment in the file
-	echo "// ${DEB_VERSION_UPSTREAM_REVISION}" > $@.tmp
-	cat ${JSSRC} ${MARKEDJS}  >> $@.tmp
+	echo "// $(DEB_VERSION_UPSTREAM_REVISION)" > $@.tmp
+	cat $(JSSRC) $(MARKEDJS)  >> $@.tmp
 	mv $@.tmp $@
 
 install: proxmoxlib.js
-	install -d -m 755 ${WWWBASEDIR}
-	install -m 0644 proxmoxlib.js ${WWWBASEDIR}
-	set -e && for i in ${SUBDIRS}; do ${MAKE} -C $$i $@; done
+	install -d -m 755 $(WWWBASEDIR)
+	install -m 0644 proxmoxlib.js $(WWWBASEDIR)
+	set -e && for i in $(SUBDIRS); do $(MAKE) -C $$i $@; done
 
 .PHONY: clean
 clean:
diff --git a/src/css/Makefile b/src/css/Makefile
index d14dbd5..e31c06f 100644
--- a/src/css/Makefile
+++ b/src/css/Makefile
@@ -5,9 +5,9 @@ CSS=ext6-pmx.css
 all:
 
 .PHONY: install
-install: ${CSS}
-	install -d ${WWWCSSDIR}
-	for i in ${CSS}; do install -m 0644 $$i ${WWWCSSDIR}/$$i; done
+install: $(CSS)
+	install -d $(WWWCSSDIR)
+	for i in $(CSS); do install -m 0644 $$i $(WWWCSSDIR)/$$i; done
 
 .PHONY: clean
 clean:
diff --git a/src/defines.mk b/src/defines.mk
index 2a65e9d..c186edc 100644
--- a/src/defines.mk
+++ b/src/defines.mk
@@ -1,6 +1,6 @@
 DESTDIR=
-DOCDIR=${DESTDIR}/usr/share/doc/${PACKAGE}
-WWWBASEDIR=${DESTDIR}/usr/share/javascript/${PACKAGE}
-WWWCSSDIR=${WWWBASEDIR}/css
-WWWIMAGESDIR=${WWWBASEDIR}/images
-WWWTHEMEDIR=${WWWBASEDIR}/themes
+DOCDIR=$(DESTDIR)/usr/share/doc/$(PACKAGE)
+WWWBASEDIR=$(DESTDIR)/usr/share/javascript/$(PACKAGE)
+WWWCSSDIR=$(WWWBASEDIR)/css
+WWWIMAGESDIR=$(WWWBASEDIR)/images
+WWWTHEMEDIR=$(WWWBASEDIR)/themes
diff --git a/src/images/Makefile b/src/images/Makefile
index 26aeed8..61395b4 100644
--- a/src/images/Makefile
+++ b/src/images/Makefile
@@ -10,9 +10,9 @@ IMAGES=pmx-clear-trigger.png		\
 all:
 
 .PHONY: install
-install: ${IMAGES}
-	install -d ${WWWIMAGESDIR}
-	for i in ${IMAGES}; do install -m 0644 $$i ${WWWIMAGESDIR}/$$i; done
+install: $(IMAGES)
+	install -d $(WWWIMAGESDIR)
+	for i in $(IMAGES); do install -m 0644 $$i $(WWWIMAGESDIR)/$$i; done
 
 .PHONY: clean
 clean:
diff --git a/src/proxmox-dark/Makefile b/src/proxmox-dark/Makefile
index 2ac6f22..467b396 100644
--- a/src/proxmox-dark/Makefile
+++ b/src/proxmox-dark/Makefile
@@ -35,10 +35,10 @@ all: theme-proxmox-dark.css
 
 .PHONY: install
 install: theme-proxmox-dark.css
-	install -d ${WWWTHEMEDIR}/
-	install -m 0664 theme-proxmox-dark.css ${WWWTHEMEDIR}/
+	install -d $(WWWTHEMEDIR)/
+	install -m 0664 theme-proxmox-dark.css $(WWWTHEMEDIR)/
 
-theme-proxmox-dark.css: ${SCSSSRC}
+theme-proxmox-dark.css: $(SCSSSRC)
 	sassc -t compressed $< $@.tmp
 	mv $@.tmp $@