diff --git a/js/src/jscntxt.cpp b/js/src/jscntxt.cpp
index 158e982dc40b..30682ab13bc6 100644
--- a/js/src/jscntxt.cpp
+++ b/js/src/jscntxt.cpp
@@ -552,7 +552,7 @@ PrintSingleError(JSContext* cx, FILE* file, JS::ConstUTF8CharsZ toStringResult,
         const char* kindPrefix = nullptr;
         switch (kind) {
           case PrintErrorKind::Error:
-            break;
+            MOZ_CRASH("unreachable");
           case PrintErrorKind::Warning:
             kindPrefix = "warning";
             break;