diff --git a/lib/Makefile b/lib/Makefile
index 02f6f7c..af6d708 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -64,7 +64,7 @@ else
 ifeq "$(TARGET)" "x86_64"
  OBJ = $(addprefix $(DIR)/,$(X86_64_O))
  TGT = -DTCC_TARGET_X86_64
- XCC ?= $(TCC) -B$(TOP)
+ XCC ?= $(TCC) -B$(TOP) -I$(includedir)
 else
  $(error libtcc1.a not supported on target '$(TARGET)')
 endif
diff --git a/lib/libtcc1.c b/lib/libtcc1.c
index b00d044..dacee28 100644
--- a/lib/libtcc1.c
+++ b/lib/libtcc1.c
@@ -609,7 +609,7 @@ unsigned long long __fixunsxfdi (long double a1)
 
 /* helper functions for stdarg.h */
 
-//#include <stdlib.h>
+#include <stdlib.h>
 #ifndef __TINYC__
 /* gives "incompatible types for redefinition of __va_arg" below */
 #include <stdio.h>
diff --git a/tests/Makefile b/tests/Makefile
index 6e0f728..ea98604 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -41,7 +41,7 @@ ifeq ($(TARGETOS),Darwin)
 endif
 
 # run local version of tcc with local libraries and includes
-TCCFLAGS = -B$(TOP)
+TCCFLAGS = -B$(TOP) -I$(includedir)
 ifdef CONFIG_WIN32
  TCCFLAGS = -B$(top_srcdir)/win32 -I$(top_srcdir)/include -L$(TOP)
 endif
diff --git a/tests/tests2/Makefile b/tests/tests2/Makefile
index bf7511f..7ee254a 100644
--- a/tests/tests2/Makefile
+++ b/tests/tests2/Makefile
@@ -2,7 +2,7 @@ TOP = ../..
 include $(TOP)/Makefile
 VPATH = $(top_srcdir)/tests/tests2
 
-TCCFLAGS = -B$(TOP)
+TCCFLAGS = -B$(TOP) -I$(includedir)
 ifdef CONFIG_WIN32
  TCCFLAGS = -B$(top_srcdir)/win32 -I$(top_srcdir)/include -L$(TOP)
 endif