diff --git a/trisquel-automatic-netinstall-qemu/Makefile.am b/trisquel-automatic-netinstall-qemu/Makefile.am
index 9ff46f3..fe4abee 100644
--- a/trisquel-automatic-netinstall-qemu/Makefile.am
+++ b/trisquel-automatic-netinstall-qemu/Makefile.am
@@ -61,7 +61,7 @@ preseed.img: Makefile preseed.cfg
 	mv $@.tmp $@
 
 rootfs.img.tmp: Makefile
-	qemu-img create -f qcow2 $@ 10G
+	qemu-img create -f qcow2 $@ $(TRISQUEL_ROOTFS_SIZE)
 
 # The 790M were found by trial and error. At 789M the netinstall
 # complains about "low memory".
diff --git a/trisquel-automatic-netinstall-qemu/configure.ac b/trisquel-automatic-netinstall-qemu/configure.ac
index dc64b95..f5d792a 100644
--- a/trisquel-automatic-netinstall-qemu/configure.ac
+++ b/trisquel-automatic-netinstall-qemu/configure.ac
@@ -22,6 +22,7 @@ AC_PROG_MKDIR_P
 AM_INIT_AUTOMAKE([foreign])
 
 AC_SUBST([ENABLE_KVM], [])
+AC_SUBST([TRISQUEL_ROOTFS_SIZE], [])
 AC_SUBST([TRISQUEL_NETINSTALL], [])
 
 AC_ARG_ENABLE(kvm,
@@ -32,6 +33,16 @@ AC_ARG_ENABLE(kvm,
 
 AM_CONDITIONAL( [WANT_KVM], [test x"$kvm" = x"yes"])
 
+AC_ARG_WITH(
+  [--with-trisquel-target-rootfs-size],
+  [AS_HELP_STRING(
+    [--trisquel-target-rootfs-size=SIZE],
+    [Size of the target image (default=3.5G). The size will be passed
+    as-is to the 'qemu-img create' command. See 'man 1 qemu-img' for
+    more details.])],
+  [TRISQUEL_ROOTFS_SIZE=$withval],
+  [TRISQUEL_ROOTFS_SIZE=3.5G]) dnl 3.4G: Fail, 3.5G: OK
+
 AC_ARG_WITH(
   [trisquel-netinstall],
   [AS_HELP_STRING(
@@ -118,3 +129,4 @@ AS_IF([test x"$kvm" = x"yes"],
       [echo "- Kvm: enabled"],
       [echo "- Kvm: disabled"])
 echo "- Trisquel netinstall path: $TRISQUEL_NETINSTALL"
+echo "- Trisquel target rootfs size: $TRISQUEL_ROOTFS_SIZE"