diff --git a/src/Makefile.in b/src/Makefile.in
index b6d56977738..b1cccf13755 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -21,7 +21,7 @@ CPP = $(CC) -E -Is -Im
 # Just to avoid uncertainty.
 SHELL = /bin/sh
 
-SUBMAKEFLAGS = CC='${CC}' LN_S='${LN_S}'
+SUBMAKEFLAGS = CC='${CC}' LN_S='${LN_S}' CFLAGS='${CFLAGS}'
 
 all: doall