diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 27c42130eb9..cfdc8b87fd7 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-04  Tom Tromey  <tom@tromey.com>
+
+	* configure: Rebuild.
+	* warning.m4 (AM_GDB_WARNINGS): Add -Wimplicit-fallthrough.
+
 2018-05-04  Tom Tromey  <tom@tromey.com>
 
 	* linux-record.c (record_linux_system_call) <case
diff --git a/gdb/configure b/gdb/configure
index 1aac9303ac3..96dd9fa7324 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -15366,7 +15366,8 @@ build_warnings="-Wall -Wpointer-arith \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
 -Wno-mismatched-tags \
 -Wno-error=deprecated-register \
--Wsuggest-override"
+-Wsuggest-override \
+-Wimplicit-fallthrough"
 
 case "${host}" in
   *-*-mingw32*)
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 4726ef4402f..f1dd1ddc977 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,7 @@
+2018-05-04  Tom Tromey  <tom@tromey.com>
+
+	* configure: Rebuild.
+
 2018-05-04  Jan Kratochvil  <jan.kratochvil@redhat.com>
 	    Pedro Alves <palves@redhat.com>
 
diff --git a/gdb/gdbserver/configure b/gdb/gdbserver/configure
index 22b4c8af682..919ed316653 100755
--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -7173,7 +7173,8 @@ build_warnings="-Wall -Wpointer-arith \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
 -Wno-mismatched-tags \
 -Wno-error=deprecated-register \
--Wsuggest-override"
+-Wsuggest-override \
+-Wimplicit-fallthrough"
 
 case "${host}" in
   *-*-mingw32*)
diff --git a/gdb/warning.m4 b/gdb/warning.m4
index f176a3291aa..1cc3c683985 100644
--- a/gdb/warning.m4
+++ b/gdb/warning.m4
@@ -43,7 +43,8 @@ build_warnings="-Wall -Wpointer-arith \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
 -Wno-mismatched-tags \
 -Wno-error=deprecated-register \
--Wsuggest-override"
+-Wsuggest-override \
+-Wimplicit-fallthrough"
 
 case "${host}" in
   *-*-mingw32*)