diff --git a/awesomeConfig.cmake b/awesomeConfig.cmake
index e05bc8c19..692eb82cb 100644
--- a/awesomeConfig.cmake
+++ b/awesomeConfig.cmake
@@ -25,7 +25,8 @@ add_definitions(-std=gnu99 -ggdb3 -fno-strict-aliasing -Wall -Wextra
     -Wchar-subscripts -Wundef -Wshadow -Wcast-align -Wwrite-strings
     -Wsign-compare -Wunused -Wno-unused-parameter -Wuninitialized -Winit-self
     -Wpointer-arith -Wredundant-decls -Wformat-nonliteral
-    -Wno-format-zero-length -Wmissing-format-attribute)
+    -Wno-format-zero-length -Wmissing-format-attribute -Wmissing-prototypes
+    -Wstrict-prototypes)
 # }}}
 
 # {{{ Find external utilities
diff --git a/widgets/progressbar.c b/widgets/progressbar.c
index b3c44b202..c37873390 100644
--- a/widgets/progressbar.c
+++ b/widgets/progressbar.c
@@ -407,7 +407,7 @@ progressbar_draw(draw_context_t *ctx,
  * \lparam A bar name.
  * \lparam A table with keys as properties names.
  */
-int
+static int
 luaA_progressbar_bar_properties_set(lua_State *L)
 {
     widget_t **widget = luaA_checkudata(L, 1, "widget");
@@ -492,7 +492,7 @@ luaA_progressbar_bar_properties_set(lua_State *L)
  * \lparam A bar name.
  * \lparam A data value.
  */
-int
+static int
 luaA_progressbar_bar_data_add(lua_State *L)
 {
     widget_t **widget = luaA_checkudata(L, 1, "widget");
diff --git a/widgets/taglist.c b/widgets/taglist.c
index 324fde2c9..ea93b0a80 100644
--- a/widgets/taglist.c
+++ b/widgets/taglist.c
@@ -293,7 +293,7 @@ taglist_button_press(widget_node_t *w,
  * \param L The Lua VM state.
  * \return The number of elements pushed on stack.
  */
-int
+static int
 luaA_taglist_index(lua_State *L)
 {
     size_t len;
@@ -324,7 +324,7 @@ luaA_taglist_index(lua_State *L)
  * \param L The Lua VM state.
  * \return The number of elements pushed on stack.
  */
-int
+static int
 luaA_taglist_newindex(lua_State *L)
 {
     size_t len;