diff --git a/internal/js_ast/js_ast_helpers.go b/internal/js_ast/js_ast_helpers.go
index da82caa4c02..c51afd335c5 100644
--- a/internal/js_ast/js_ast_helpers.go
+++ b/internal/js_ast/js_ast_helpers.go
@@ -929,6 +929,11 @@ func ToInt32(f float64) int32 {
 		return i
 	}
 
+	// Special-case non-finite numbers (casting them is unspecified behavior in Go)
+	if math.IsNaN(f) || math.IsInf(f, 0) {
+		return 0
+	}
+
 	// The hard way
 	i = int32(uint32(math.Mod(math.Abs(f), 4294967296)))
 	if math.Signbit(f) {
diff --git a/internal/js_parser/js_parser_test.go b/internal/js_parser/js_parser_test.go
index e2ae3d9674a..6487fc55fc5 100644
--- a/internal/js_parser/js_parser_test.go
+++ b/internal/js_parser/js_parser_test.go
@@ -3679,6 +3679,8 @@ func TestMangleCharCodeAt(t *testing.T) {
 	expectPrintedMangle(t, "a = '🧀'.charCodeAt(2)", "a = NaN;\n")
 
 	expectPrintedMangle(t, "a = 'xy'.charCodeAt(NaN)", "a = \"xy\".charCodeAt(NaN);\n")
+	expectPrintedMangle(t, "a = 'xy'.charCodeAt(-Infinity)", "a = \"xy\".charCodeAt(-Infinity);\n")
+	expectPrintedMangle(t, "a = 'xy'.charCodeAt(Infinity)", "a = \"xy\".charCodeAt(Infinity);\n")
 	expectPrintedMangle(t, "a = 'xy'.charCodeAt(0.5)", "a = \"xy\".charCodeAt(0.5);\n")
 	expectPrintedMangle(t, "a = 'xy'.charCodeAt(1e99)", "a = \"xy\".charCodeAt(1e99);\n")
 	expectPrintedMangle(t, "a = 'xy'.charCodeAt('1')", "a = \"xy\".charCodeAt(\"1\");\n")
@@ -3697,6 +3699,7 @@ func TestMangleFromCharCode(t *testing.T) {
 	expectPrintedMangle(t, "a = String.fromCharCode(0x10078, 0x10079)", "a = \"xy\";\n")
 	expectPrintedMangle(t, "a = String.fromCharCode(0x1_0000_FFFF)", "a = \"\uFFFF\";\n")
 	expectPrintedMangle(t, "a = String.fromCharCode(NaN)", "a = \"\\0\";\n")
+	expectPrintedMangle(t, "a = String.fromCharCode(-Infinity)", "a = \"\\0\";\n")
 	expectPrintedMangle(t, "a = String.fromCharCode(Infinity)", "a = \"\\0\";\n")
 	expectPrintedMangle(t, "a = String.fromCharCode(null)", "a = \"\\0\";\n")
 	expectPrintedMangle(t, "a = String.fromCharCode(undefined)", "a = \"\\0\";\n")