diff --git a/js/src/jsemit.h b/js/src/jsemit.h
index 10333ca2142..fda43ebae16 100644
--- a/js/src/jsemit.h
+++ b/js/src/jsemit.h
@@ -261,7 +261,7 @@ struct JSTreeContext {              /* tree context for semantic checks */
 #define TCF_HAS_SHARPS        0x8000 /* source contains sharp defs or uses */
 
 /*
- * Flags to propagate from FunctionBody.
+ * Sticky deoptimization flags to propagate from FunctionBody.
  */
 #define TCF_FUN_FLAGS           (TCF_FUN_SETS_OUTER_NAME |                    \
                                  TCF_FUN_USES_ARGUMENTS  |                    \
diff --git a/js/src/jsparse.cpp b/js/src/jsparse.cpp
index 39d0d275497..e46aca9f148 100644
--- a/js/src/jsparse.cpp
+++ b/js/src/jsparse.cpp
@@ -6405,9 +6405,15 @@ GeneratorExpr(JSParseNode *pn, JSParseNode *kid, JSTreeContext *tc)
         if (!funbox)
             return NULL;
 
-        gentc.flags |= TCF_FUN_IS_GENERATOR | TCF_GENEXP_LAMBDA;
-        if (tc->flags & TCF_HAS_SHARPS)
-            gentc.flags |= TCF_HAS_SHARPS;
+        /*
+         * We assume conservatively that any deoptimization flag in tc->flags
+         * besides TCF_FUN_PARAM_ARGUMENTS can come from the kid. So we
+         * propagate these flags into genfn. For code simplicity we also do
+         * not detect if the flags were only set in the kid and could be
+         * removed from tc->flags.
+         */
+        gentc.flags |= TCF_FUN_IS_GENERATOR | TCF_GENEXP_LAMBDA |
+                       (tc->flags & (TCF_FUN_FLAGS & ~TCF_FUN_PARAM_ARGUMENTS));
         funbox->tcflags |= gentc.flags;
         genfn->pn_funbox = funbox;
         genfn->pn_blockid = gentc.bodyid;