diff --git a/Makefile.mk b/Makefile.mk
index d55d1a49e..73f2759fb 100644
--- a/Makefile.mk
+++ b/Makefile.mk
@@ -190,7 +190,7 @@ CFLAGS_WERROR ?= -Werror
 CFLAGS_WFATAL_ERRORS ?= -Wfatal-errors
 
 # Optimizations
-CFLAGS_OPTIMIZE ?= -Os -flto
+CFLAGS_OPTIMIZE ?= -O3 -flto
 CFLAGS_NO_OPTIMIZE ?= -O0
 LDFLAGS_OPTIMIZE ?=
 LDFLAGS_NO_OPTIMIZE ?=
diff --git a/src/libjsparser/parser.c b/src/libjsparser/parser.c
index ca12d9d3b..cc3b25891 100644
--- a/src/libjsparser/parser.c
+++ b/src/libjsparser/parser.c
@@ -2847,7 +2847,7 @@ parse_while_statement (void)
 
   STACK_PUSH (U16, OPCODE_COUNTER ());
   DUMP_OPCODE_2 (jmp_up, INVALID_VALUE, INVALID_VALUE);
-  REWRITE_JMP (STACK_TOP (U16), jmp_up, OPCODE_COUNTER () - STACK_HEAD (U16, 3));
+  REWRITE_JMP (STACK_TOP (U16), jmp_up, STACK_TOP (U16) - STACK_HEAD (U16, 3));
   REWRITE_COND_JMP (STACK_HEAD (U16, 2), is_false_jmp_down, OPCODE_COUNTER () - STACK_HEAD (U16, 2));
 
   rewrite_rewritable_opcodes (REWRITABLE_CONTINUE, STACK_HEAD (U8, 2), STACK_HEAD (U16, 3));
diff --git a/src/liboptimizer/pretty-printer.c b/src/liboptimizer/pretty-printer.c
index 0de99865b..d2cd2057a 100644
--- a/src/liboptimizer/pretty-printer.c
+++ b/src/liboptimizer/pretty-printer.c
@@ -276,7 +276,7 @@ pp_opcode (opcode_counter_t oc, opcode_t opcode, bool is_rewrite)
     }
     case NAME_TO_ID (is_false_jmp_down):
     {
-      pp_printf ("if (%s) goto %d;", opcode.data.is_false_jmp_down.value,
+      pp_printf ("if (%s == false) goto %d;", opcode.data.is_false_jmp_down.value,
                  oc + calc_opcode_counter_from_idx_idx (opcode.data.is_false_jmp_down.opcode_1,
                                                         opcode.data.is_false_jmp_down.opcode_2));
       break;