diff --git a/tests/src/test_cases/draw/test_image_formats.c b/tests/src/test_cases/draw/test_image_formats.c
index d4971a533e94..91861508ef0d 100644
--- a/tests/src/test_cases/draw/test_image_formats.c
+++ b/tests/src/test_cases/draw/test_image_formats.c
@@ -275,7 +275,7 @@ static void c_array_image_create(bool rotate, bool recolor, int align, int compr
     }
 }
 
-void test_image_formats()
+void test_image_formats(void)
 {
     for(unsigned align = 0; align <= 1; align++) {
         int stride = stride_align[align];
diff --git a/tests/src/test_cases/libs/test_tiny_ttf.c b/tests/src/test_cases/libs/test_tiny_ttf.c
index 2ec1fde11ab0..b725081d38ac 100644
--- a/tests/src/test_cases/libs/test_tiny_ttf.c
+++ b/tests/src/test_cases/libs/test_tiny_ttf.c
@@ -46,7 +46,7 @@ void test_tiny_ttf_rendering_test(void)
 #endif
 }
 
-void test_tiny_ttf_kerning()
+void test_tiny_ttf_kerning(void)
 {
 #if LV_USE_TINY_TTF
     extern const uint8_t test_kern_one_otf[];