diff --git a/Makefile.mk b/Makefile.mk
index 3a6fbd097..d8e2ee3fe 100644
--- a/Makefile.mk
+++ b/Makefile.mk
@@ -207,7 +207,7 @@ TARGET_CPU = $(strip $(if $(filter linux,$(TARGET_SYSTEM)), x64, \
 CFLAGS_WARNINGS ?= -Wall -Wextra -Wpedantic -Wlogical-op -Winline \
                    -Wformat-nonliteral -Winit-self -Wstack-protector \
                    -Wconversion -Wsign-conversion -Wformat-security \
-                   -Wno-attributes
+                   -Wmissing-declarations -Wno-attributes
 CFLAGS_WERROR ?= -Werror
 CFLAGS_WFATAL_ERRORS ?= -Wfatal-errors
 
diff --git a/src/libecmaobjects/ecma-helpers-values-collection.c b/src/libecmaobjects/ecma-helpers-values-collection.c
index 5aa41d745..46251eb6a 100644
--- a/src/libecmaobjects/ecma-helpers-values-collection.c
+++ b/src/libecmaobjects/ecma-helpers-values-collection.c
@@ -31,7 +31,7 @@
  * @return pointer to the collection's header
  */
 ecma_collection_header_t*
-ecma_new_values_collection (ecma_value_t values_buffer[], /**< ecma-values */
+ecma_new_values_collection (const ecma_value_t values_buffer[], /**< ecma-values */
                             ecma_length_t values_number, /**< number of ecma-values */
                             bool do_ref_if_object) /**< if the value is object value,
                                                         increase reference counter of the object */