diff --git a/mingw-w64-tools/gendef/src/gendef.c b/mingw-w64-tools/gendef/src/gendef.c
index a935abfe..cefdd8cb 100644
--- a/mingw-w64-tools/gendef/src/gendef.c
+++ b/mingw-w64-tools/gendef/src/gendef.c
@@ -1031,13 +1031,16 @@ redo_switch:
     PRDEBUG(" 0x%x illegal ", (unsigned int) b);
 #endif
     *aCode=c_ill; return 0;
-  case c_4: sz++;
-  case c_3: sz++;
-  case c_lb:
-  case c_2: sz++;
-  case c_retn: case c_retf:
-  case c_iret: case c_int3:
-  case c_ad: case c_op:
+  case c_4: sz++; // fallthrough
+  case c_3: sz++; // fallthrough
+  case c_lb: // fallthrough
+  case c_2: sz++; // fallthrough
+  case c_retn: // fallthrough
+  case c_retf: // fallthrough
+  case c_iret: // fallthrough
+  case c_int3: // fallthrough
+  case c_ad: // fallthrough
+  case c_op: // fallthrough
   case c_1: *aCode=tb1; return sz;
   case c_lv:
     if (oper_mode) sz+=4;
diff --git a/mingw-w64-tools/genpeimg/src/genpeimg.c b/mingw-w64-tools/genpeimg/src/genpeimg.c
index b2430bbc..6a37b1a0 100644
--- a/mingw-w64-tools/genpeimg/src/genpeimg.c
+++ b/mingw-w64-tools/genpeimg/src/genpeimg.c
@@ -203,7 +203,7 @@ pass_args (int argc, char **argv)
 	  goto error_point;
 	case 'h':
 	  if (h[2] == 0)
-	    show_usage ();
+	    show_usage (); // fallthrough
 	default:
 error_point:
 	  fprintf (stderr, "Unknown option ,%s'\n", h);