diff --git a/makefile b/makefile
index a2e61f2..217efc4 100644
--- a/makefile
+++ b/makefile
@@ -15,7 +15,7 @@ ifeq ($(LOG_USE_COLOR), yes)
 else
 	CPPFLAGS := -Iinclude -MMD -MP
 endif
-CFLAGS = -O -Wall -W -pedantic -ansi -std=c99
+CFLAGS = -O -Wall -W -pedantic -ansi -std=c2x
 LDFLAGS  := -Llib
 LDLIBS   := -lm
 
diff --git a/src/vmrcli.c b/src/vmrcli.c
index f86bec2..268f178 100644
--- a/src/vmrcli.c
+++ b/src/vmrcli.c
@@ -136,7 +136,7 @@ int main(int argc, char *argv[])
                      optopt);
             exit(EXIT_FAILURE);
         case 'h':
-            /* FALLTHROUGH */
+            [[fallthrough]];
         default:
             usage();
         }