diff --git a/m4/gccwarn.m4 b/m4/gccwarn.m4
index bfb3da957..8d1a53e1b 100644
--- a/m4/gccwarn.m4
+++ b/m4/gccwarn.m4
@@ -37,6 +37,7 @@ EOF
    Wnoexcept \
    Woverloaded-virtual \
    Wmisleading-indentation \
+   Wimplicit-fallthrough \
    Wlogical-op \
    Wduplicated-cond \
    Wnull-dereference \