diff --git a/32/Makefile b/32/Makefile
index 85cb464..1f1fb85 100644
--- a/32/Makefile
+++ b/32/Makefile
@@ -4,8 +4,8 @@ DOS_CC ?= i586-pc-msdosdjgpp-gcc
 DOS_LD ?= i586-pc-msdosdjgpp-gcc
 DOS_AS ?= i586-pc-msdosdjgpp-as
 DOS_STRIP ?= i586-pc-msdosdjgpp-strip
-PREFIX ?= /usr/local
-DATADIR ?= $(PREFIX)/share/comcom32
+prefix ?= /usr/local
+DATADIR ?= $(prefix)/share/comcom32
 C_OPT = -Wall -O2 -Wmissing-declarations -Wwrite-strings -I $(SRCDIR) -I .
 # avoid CMOVxx instructions
 C_OPT += -march=i386
diff --git a/comcom64.spec.rpkg b/comcom64.spec.rpkg
index 6c65f19..effa26f 100644
--- a/comcom64.spec.rpkg
+++ b/comcom64.spec.rpkg
@@ -38,7 +38,7 @@ make %{?_smp_mflags}
 %define __strip /bin/true
 
 %install
-make install DESTDIR=%{buildroot} PREFIX=%{_prefix}
+make install DESTDIR=%{buildroot} prefix=%{_prefix}
 
 %files
 %defattr(-,root,root)
diff --git a/debian/rules b/debian/rules
index 889fe49..3e6b621 100755
--- a/debian/rules
+++ b/debian/rules
@@ -4,4 +4,4 @@
 	dh $@
 
 override_dh_auto_install:
-	dh_auto_install $@ -- PREFIX=/usr
\ No newline at end of file
+	dh_auto_install $@ -- prefix=/usr
\ No newline at end of file
diff --git a/src/Makefile b/src/Makefile
index b864437..b9d5fb6 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,5 +1,5 @@
-PREFIX ?= /usr/local
-DATADIR ?= $(PREFIX)/share/comcom64
+prefix ?= /usr/local
+DATADIR ?= $(prefix)/share/comcom64
 CFLAGS = -Wall -Os -Wmissing-declarations -Wwrite-strings \
   -ggdb3 -Wunused -Wmissing-prototypes
 SOURCES = command.c cmdbuf.c mouse.c env.c psp.c umb.c ae0x.c compl.c clip.c \
@@ -45,7 +45,7 @@ uninstall:
 	rm -rf $(DATADIR)
 
 # hook in dj64 - make sure to not do that before defining `all:` target
-export PKG_CONFIG_PATH = $(PREFIX)/share/pkgconfig:$(PREFIX)/lib/pkgconfig
+export PKG_CONFIG_PATH = $(prefix)/share/pkgconfig:$(prefix)/lib/pkgconfig
 DJMK = $(shell pkg-config --variable=makeinc dj64)
 ifeq ($(wildcard $(DJMK)),)
 ifeq ($(filter clean,$(MAKECMDGOALS)),)