diff --git a/src/Makefile b/src/Makefile
index 41cef2a17..539c2fa74 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