diff --git a/src/Makefile b/src/Makefile
index 539c2fa743cc46071c94b8736c49802e6034e62c..41cef2a179383670247847bcd572a651c1b8aad6 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -141,9 +141,9 @@ endif
 
 OBJDUMP_OPTS?=--wide --source --line-numbers
 
-OBJCOPY?=$(call Prefix,objcopy)
-OBJDUMP?=$(call Prefix,objdump)
-WINDRES?=$(call Prefix,windres)
+OBJCOPY:=$(call Prefix,objcopy)
+OBJDUMP:=$(call Prefix,objdump)
+WINDRES:=$(call Prefix,windres)
 
 GZIP?=gzip
 GZIP_OPTS?=-9 -f -n