--- old/src/java.base/share/classes/java/math/BigInteger.java	2019-08-22 10:35:32.000000000 -0700
+++ new/src/java.base/share/classes/java/math/BigInteger.java	2019-08-22 10:35:31.000000000 -0700
@@ -3960,6 +3960,19 @@
         return sb.toString();
     }
 
+    private static void padWithZeros(StringBuilder buf, int len, int digits) {
+        if (digits > 0 && len < digits) {
+            int m = digits - len;
+            while (m >= NUM_ZEROS) {
+                buf.append(ZEROS);
+                m -= NUM_ZEROS;
+            }
+            if (m > 0) {
+                buf.append(ZEROS, 0, m);
+            }
+        }
+    }
+
     /**
      * This method is used to perform toString when arguments are small.
      * A negative sign will be prepended if and only if {@code this < 0}.
@@ -3973,6 +3986,7 @@
     private void smallToString(int radix, StringBuilder buf, int digits) {
         if (signum == 0) {
             buf.append('0');
+            padWithZeros(buf, 1, digits);
             return;
         }
 
@@ -4006,19 +4020,8 @@
         String s = Long.toString(digitGroups[numGroups-1], radix);
 
         // Pad with internal zeros if necessary.
-        if (digits > 0) {
-            int len = s.length() + (numGroups - 1)*digitsPerLong[radix];
-            if (len < digits) {
-                int m = digits - len;
-                while (m >= NUM_ZEROS) {
-                    buf.append(zeros);
-                    m -= NUM_ZEROS;
-                }
-                if (m > 0) {
-                    buf.append(zeros, 0, m);
-                }
-            }
-        }
+        padWithZeros(buf, s.length() + (numGroups - 1)*digitsPerLong[radix],
+            digits);
 
         // Put first digit group into result buffer
         buf.append(s);
@@ -4029,7 +4032,7 @@
             s = Long.toString(digitGroups[i], radix);
             int numLeadingZeros = digitsPerLong[radix] - s.length();
             if (numLeadingZeros != 0) {
-                buf.append(zeros, 0, numLeadingZeros);
+                buf.append(ZEROS, 0, numLeadingZeros);
             }
             buf.append(s);
         }
@@ -4114,11 +4117,11 @@
         return cacheLine[exponent];
     }
 
-    /* Size of zeros string. */
+    /* Size of ZEROS string. */
     private static int NUM_ZEROS = 63;
 
-    /* zero is a string of NUM_ZEROS consecutive zeros. */
-    private static final String zeros = "0".repeat(NUM_ZEROS);
+    /* ZEROS is a string of NUM_ZEROS consecutive zeros. */
+    private static final String ZEROS = "0".repeat(NUM_ZEROS);
 
     /**
      * Returns the decimal String representation of this BigInteger.