diff --git a/Objects/complexobject.c b/Objects/complexobject.c
index 4c6ea39..0d37fb2 100644
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -274,16 +274,16 @@
 {
 	char format[32];
 	if (v->cval.real == 0.) {
-		PyOS_snprintf(format, 32, "%%.%ig", precision);
-		PyOS_ascii_formatd(buf, bufsz, format, v->cval.imag);
-		strncat(buf, "j", bufsz);
+		PyOS_snprintf(format, sizeof(format), "%%.%ig", precision);
+		PyOS_ascii_formatd(buf, bufsz - 1, format, v->cval.imag);
+		strncat(buf, "j", 1);
 	} else {
 		char re[64], im[64];
 		/* Format imaginary part with sign, real part without */
-		PyOS_snprintf(format, 32, "%%.%ig", precision);
-		PyOS_ascii_formatd(re, 64, format, v->cval.real);
-		PyOS_snprintf(format, 32, "%%+.%ig", precision);
-		PyOS_ascii_formatd(im, 64, format, v->cval.imag);
+		PyOS_snprintf(format, sizeof(format), "%%.%ig", precision);
+		PyOS_ascii_formatd(re, sizeof(re), format, v->cval.real);
+		PyOS_snprintf(format, sizeof(format), "%%+.%ig", precision);
+		PyOS_ascii_formatd(im, sizeof(im), format, v->cval.imag);
 		PyOS_snprintf(buf, bufsz, "(%s%sj)", re, im);
 	}
 }