diff --git a/jv_dtoa.c b/jv_dtoa.c
index 251a6916..b8325267 100644
--- a/jv_dtoa.c
+++ b/jv_dtoa.c
@@ -4225,7 +4225,7 @@ jvp_dtoa
 		while((*b++ = *s++));
 		goto done0;
 		}
-	if (decpt <= -4 || decpt > se - s + 5) {
+	if (decpt <= -4 || decpt > se - s + 15) {
 		*b++ = *s++;
 		if (*s) {
 			*b++ = '.';
diff --git a/jv_dtoa.h b/jv_dtoa.h
index 3bafcf47..7aa5f08a 100644
--- a/jv_dtoa.h
+++ b/jv_dtoa.h
@@ -17,6 +17,6 @@ double jvp_strtod(struct dtoa_context* C, const char* s, char** se);
 char* jvp_dtoa(struct dtoa_context* C, double dd, int mode, int ndigits, int *decpt, int *sign, char **rve);
 void jvp_freedtoa(struct dtoa_context* C, char *s);
 
-#define JVP_DTOA_FMT_MAX_LEN 32
+#define JVP_DTOA_FMT_MAX_LEN 64
 char* jvp_dtoa_fmt(struct dtoa_context* C, register char *b, double x);
 #endif