diff --git a/3rdparty/Makefile b/3rdparty/Makefile
index 883f5dae..8f3733b1 100644
--- a/3rdparty/Makefile
+++ b/3rdparty/Makefile
@@ -114,7 +114,7 @@ TIFFSIGURL = $(TIFFURL).sig
 TIFFURLALT = $(LIBTIFFURLALT)
 TIFFPATCHES = $(LIBTIFFPATCHES)
 ZLIBVER=$(LATESTZLIBVER)
-LATESTZLIBVER = $(shell curl -s -S https://www.zlib.net/ChangeLog.txt |grep "Changes in" |head -n1|sed 's/Changes in \([0-9.]*\).*/\1/')
+LATESTZLIBVER := $(shell curl -s -S https://www.zlib.net/ChangeLog.txt |grep "Changes in" |head -n1|sed 's/Changes in \([0-9.]*\).*/\1/')
 ZLIB=zlib-$(ZLIBVER)
 ZLIBARCH=$(ZLIB).tar.gz
 ZLIBSIG=$(ZLIBARCH).asc
@@ -128,7 +128,7 @@ FREETYPESIG=$(FREETYPEARCH).sig
 FREETYPEURL=https://download.savannah.gnu.org/releases/freetype/$(FREETYPEARCH)
 FREETYPEURLALT=https://sourceforge.net/projects/freetype/files/freetype2/$(FREETYPEVER)/$(FREETYPEARCH)
 FREETYPESIGURL=$(FREETYPEURL).sig
-LATESTFREETYPEVER = $(shell curl -s -S -I "https://sourceforge.net/projects/freetype/files/latest/download" |grep -i '^location:' | sed 's:.*/\([0-9.]*\)/.*:\1:' )
+LATESTFREETYPEVER := $(shell curl -s -S -I "https://sourceforge.net/projects/freetype/files/latest/download" |grep -i '^location:' | sed 's:.*/\([0-9.]*\)/.*:\1:' )
 LUAVER=5.3.6
 LUA=lua-$(LUAVER)
 LUAARCH=$(LUA).tar.gz