diff --git a/CUtils/c_sources/Makefile.PL b/CUtils/c_sources/Makefile.PL
index 6e89bc102a77d519d1155a5839e0a3cbb59c00c7..5bc2d53e2a5d6d7bc64af03a000e2cae21bca788 100644
--- a/CUtils/c_sources/Makefile.PL
+++ b/CUtils/c_sources/Makefile.PL
@@ -5,7 +5,7 @@ WriteMakefile(
     NAME   => 'ALTree::CUtils',
     SKIP   => [qw(all static static_lib dynamic dynamic_lib)],
     clean  => {'FILES' => 'libaltree-cutils$(LIB_EXT)'},
-    INC               => '-I. -Ic_sources',
+    INC    => '-Wall -I. -Ic_sources',
 );
 
 sub MY::top_targets {