diff --git a/plugins/sudoers/Makefile.in b/plugins/sudoers/Makefile.in
index cd4b52846..5061b4943 100644
--- a/plugins/sudoers/Makefile.in
+++ b/plugins/sudoers/Makefile.in
@@ -50,7 +50,7 @@ SUDOERS_LIBS = @SUDOERS_LIBS@ @AFS_LIBS@ @GETGROUPS_LIB@ $(LIBS) $(NET_LIBS) @ZL
 REPLAY_LIBS = @REPLAY_LIBS@ @ZLIB@
 
 # C preprocessor flags
-CPPFLAGS = -I$(incdir) -I$(top_builddir) -I$(srcdir) @CPPFLAGS@
+CPPFLAGS = -I$(incdir) -I$(top_builddir) -I$(srcdir) -I$(top_srcdir) @CPPFLAGS@
 
 # Usually -O and/or -g
 CFLAGS = @CFLAGS@