diff --git a/lib/filehighlight/ini-file-read.c b/lib/filehighlight/ini-file-read.c
index 7f4dde26b..a3f9dcd5a 100644
--- a/lib/filehighlight/ini-file-read.c
+++ b/lib/filehighlight/ini-file-read.c
@@ -38,8 +38,6 @@
 
 /*** global variables ****************************************************************************/
 
-extern mc_skin_t mc_skin__default;
-
 /*** file scope macro definitions ****************************************************************/
 
 /*** file scope type declarations ****************************************************************/
diff --git a/lib/skin/internal.h b/lib/skin/internal.h
index cb02bf7e4..c12b34105 100644
--- a/lib/skin/internal.h
+++ b/lib/skin/internal.h
@@ -20,8 +20,6 @@ typedef struct mc_skin_color_struct
 
 /*** global variables defined in .c file *********************************************************/
 
-extern mc_skin_t mc_skin__default;
-
 /*** declarations of public functions ************************************************************/
 
 gboolean mc_skin_ini_file_load (mc_skin_t *);
diff --git a/lib/tty/tty-slang.c b/lib/tty/tty-slang.c
index db5375fbf..dfb0fa8e9 100644
--- a/lib/tty/tty-slang.c
+++ b/lib/tty/tty-slang.c
@@ -57,8 +57,6 @@
 
 /*** global variables ****************************************************************************/
 
-extern int reset_hp_softkeys;
-
 /*** file scope macro definitions ****************************************************************/
 
 #ifndef SLTT_MAX_SCREEN_COLS
diff --git a/m4.include/mc-cflags.m4 b/m4.include/mc-cflags.m4
index 30922cef8..8831ae40d 100644
--- a/m4.include/mc-cflags.m4
+++ b/m4.include/mc-cflags.m4
@@ -63,6 +63,7 @@ dnl    MC_CHECK_ONE_CFLAG([-Wbad-function-cast])
     MC_CHECK_ONE_CFLAG([-Wno-unreachable-code])
     MC_CHECK_ONE_CFLAG([-Wparentheses])
     MC_CHECK_ONE_CFLAG([-Wpointer-sign])
+    MC_CHECK_ONE_CFLAG([-Wredundant-decls])
     MC_CHECK_ONE_CFLAG([-Wreturn-type])
     MC_CHECK_ONE_CFLAG([-Wsequence-point])
     MC_CHECK_ONE_CFLAG([-Wshadow])