diff --git a/configure.ac b/configure.ac
index ccd0a5576f..9b83a215d2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -10,6 +10,7 @@ AC_CONFIG_HEADERS([config.h])
 # Checks for programs.
 AC_PROG_CXX
 AC_PROG_CC
+AM_PROG_CC_C_O
 PKG_PROG_PKG_CONFIG
 
 # Checks for libraries.
diff --git a/src/Makefile.am b/src/Makefile.am
index 6fcc0d832c..6fecfc7b86 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,3 +1,5 @@
+AUTOMAKE_OPTIONS = subdir-objects
+
 AM_CFLAGS = -Wall -std=c99
 
 bin_PROGRAMS = cbootimage bct_dump