diff --git a/BUILD/SETUP.sh b/BUILD/SETUP.sh
index 7e6f0831423..6cf2a18404c 100755
--- a/BUILD/SETUP.sh
+++ b/BUILD/SETUP.sh
@@ -141,7 +141,7 @@ elif [ "x$warning_mode" = "xmaintainer" ]; then
   debug_extra_cflags="-g3"
 else
 # Both C and C++ warnings
-  warnings="-Wall -Wextra -Wunused -Wwrite-strings -Wno-uninitialized -Wno-strict-aliasing"
+  warnings="-Wall -Wextra -Wunused -Wwrite-strings -Wno-uninitialized -Wno-strict-aliasing -Wimplicit-fallthrough=2"
 
 # For more warnings, uncomment the following line
 # warnings="$warnings -Wshadow"
diff --git a/pcre/pcre_dfa_exec.c b/pcre/pcre_dfa_exec.c
index f333381d088..830c4e4be48 100644
--- a/pcre/pcre_dfa_exec.c
+++ b/pcre/pcre_dfa_exec.c
@@ -2198,6 +2198,7 @@ for (;;)
         case 0x2029:
 #endif  /* Not EBCDIC */
         if ((md->moptions & PCRE_BSR_ANYCRLF) != 0) break;
+        /* fall through */
 
         case CHAR_LF:
         ADD_NEW(state_offset + 1, 0);
diff --git a/pcre/pcre_exec.c b/pcre/pcre_exec.c
index 93256d32455..88a9a79e489 100644
--- a/pcre/pcre_exec.c
+++ b/pcre/pcre_exec.c
@@ -2086,7 +2086,7 @@ for (;;)
     case OP_CIRC:
     if (md->notbol && eptr == md->start_subject) RRETURN(MATCH_NOMATCH);
 
-    /* Start of subject assertion */
+    /* Fall through. Start of subject assertion */
 
     case OP_SOD:
     if (eptr != md->start_subject) RRETURN(MATCH_NOMATCH);
diff --git a/pcre/pcregrep.c b/pcre/pcregrep.c
index 79d9e286c75..22c43bcda00 100644
--- a/pcre/pcregrep.c
+++ b/pcre/pcregrep.c
@@ -2407,7 +2407,7 @@ handle_option(int letter, int options)
 switch(letter)
   {
   case N_FOFFSETS: file_offsets = TRUE; break;
-  case N_HELP: help(); pcregrep_exit(0);
+  case N_HELP: help(); pcregrep_exit(0); break;
   case N_LBUFFER: line_buffered = TRUE; break;
   case N_LOFFSETS: line_offsets = number = TRUE; break;
   case N_NOJIT: study_options &= ~PCRE_STUDY_JIT_COMPILE; break;