diff --git a/src/duk_api_codec.c b/src/duk_api_codec.c
index 72c82f3c..957280ab 100644
--- a/src/duk_api_codec.c
+++ b/src/duk_api_codec.c
@@ -258,8 +258,8 @@ void duk_hex_encode(duk_context *ctx, int index) {
 
 	for (i = 0; i < len; i++) {
 		t = data[i];
-		buf[i*2 + 0] = duk_lc_nybbles[t >> 4];
-		buf[i*2 + 1] = duk_lc_nybbles[t & 0x0f];
+		buf[i*2 + 0] = duk_lc_digits[t >> 4];
+		buf[i*2 + 1] = duk_lc_digits[t & 0x0f];
 	}
 
 	duk_to_string(ctx, -1);
diff --git a/src/duk_builtin_json.c b/src/duk_builtin_json.c
index 6e1e4e1a..f7716709 100644
--- a/src/duk_builtin_json.c
+++ b/src/duk_builtin_json.c
@@ -627,7 +627,7 @@ static void json_emit_esc(duk_json_enc_ctx *js_ctx, duk_u32 cp, char *esc_str, i
 	while (digits > 0) {
 		digits--;
 		dig = (cp >> (4 * digits)) & 0x0f;
-		duk_hbuffer_append_byte(js_ctx->thr, js_ctx->h_buf, duk_lc_nybbles[dig]);
+		duk_hbuffer_append_byte(js_ctx->thr, js_ctx->h_buf, duk_lc_digits[dig]);
 	}
 }
 
@@ -1254,8 +1254,8 @@ static void json_enc_value2(duk_json_enc_ctx *js_ctx) {
 			EMIT_1(js_ctx, '|');
 			while (p < p_end) {
 				x = (int) *p++;
-				duk_hbuffer_append_byte(js_ctx->thr, js_ctx->h_buf, duk_lc_nybbles[(x >> 4) & 0x0f]);
-				duk_hbuffer_append_byte(js_ctx->thr, js_ctx->h_buf, duk_lc_nybbles[x & 0x0f]);
+				duk_hbuffer_append_byte(js_ctx->thr, js_ctx->h_buf, duk_lc_digits[(x >> 4) & 0x0f]);
+				duk_hbuffer_append_byte(js_ctx->thr, js_ctx->h_buf, duk_lc_digits[x & 0x0f]);
 			}
 			EMIT_1(js_ctx, '|');
 		} else {
diff --git a/src/duk_util.h b/src/duk_util.h
index 188eb160..f21d6bfb 100644
--- a/src/duk_util.h
+++ b/src/duk_util.h
@@ -40,7 +40,7 @@ struct duk_bitencoder_ctx {
  *  Externs and prototypes
  */
 
-extern char duk_lc_nybbles[16];
+extern char duk_lc_digits[36];
 extern char duk_uc_nybbles[16];
 
 /* Note: assumes that duk_util_probe_steps size is 32 */
diff --git a/src/duk_util_misc.c b/src/duk_util_misc.c
index 05dc0ed5..b0055e92 100644
--- a/src/duk_util_misc.c
+++ b/src/duk_util_misc.c
@@ -4,8 +4,14 @@
 
 #include "duk_internal.h"
 
-char duk_lc_nybbles[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
-                            '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
+/* Lowercase digits for radix values 2 to 36.  Also doubles as lowercase
+ * hex nybble table.
+ */
+char duk_lc_digits[36] = { '0', '1', '2', '3', '4', '5', '6', '7',
+                           '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
+                           'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+                           'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
+                           'w', 'x', 'y', 'z' };
 
 char duk_uc_nybbles[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
                             '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
diff --git a/testcases/test-numconv-tostring-fastpath.js b/testcases/test-numconv-tostring-fastpath.js
new file mode 100644
index 00000000..8357a871
--- /dev/null
+++ b/testcases/test-numconv-tostring-fastpath.js
@@ -0,0 +1,398 @@
+/*
+ *  Test the 32-bit fast path which applies to integers in the
+ *  range [-2**32-1,2**32-1], in any radix.
+ *
+ *  The test is not exhaustive but has a pretty large (prime)
+ *  skip; both endpoint values are always included though.
+ */
+
+/* FIXME: util */
+/* Trivial string checksum used to summarize brute force output lines
+ * (minimizes test case size).
+ */
+function checkSumString(x) {
+    var i, n;
+    var res = 0;
+    var mult = [ 1, 3, 5, 7, 11, 13, 17, 19, 23 ];
+
+    n = x.length;
+    for (i = 0; i < n; i++) {
+        res += x.charCodeAt(i) * mult[i % mult.length];
+        res = res >>> 0;  // coerce to 32 bits
+    }
+
+    return res;
+}
+
+/*---
+{
+    "custom": true
+}
+---*/
+
+/*===
+radix 2
+179306267
+178417689
+172469437
+158113487
+164522390
+171053804
+173839346
+73212146
+radix 3
+120001562
+116340620
+114838710
+104289556
+107366288
+110915012
+112538566
+49058085
+radix 4
+93996707
+93956672
+93119252
+85264205
+87138494
+90633905
+90749467
+38267839
+radix 5
+85524532
+85420528
+83386734
+75416390
+76399706
+79977948
+80054256
+33672687
+radix 6
+80375401
+79136945
+75214944
+69706448
+69994308
+72423839
+75586644
+31904527
+radix 7
+75660318
+75401474
+70356910
+65459640
+64698752
+68090646
+70718420
+29706955
+radix 8
+70760327
+70625152
+69485827
+61898015
+62283468
+65132380
+65228960
+27580869
+radix 9
+69419812
+65527610
+65200854
+59988264
+60261022
+60887826
+62388478
+27476559
+radix 10
+65687102
+65545878
+64772404
+57882489
+57783900
+60948995
+61112511
+25716773
+radix 11
+69166623
+68000038
+64211306
+59710995
+59000300
+61402648
+64314472
+27317298
+radix 12
+67632900
+67294827
+66690879
+60164747
+60799276
+62204906
+62065132
+26522442
+radix 13
+69740341
+69516644
+68895103
+62262756
+60104065
+64690764
+64292443
+27542684
+radix 14
+71598398
+72081748
+68929359
+62685443
+57389876
+65748807
+66567837
+28755782
+radix 15
+72430006
+71848282
+67985208
+62706717
+58859470
+59698249
+66875878
+28526129
+radix 16
+73769135
+70397366
+68140205
+62925422
+60428538
+60547551
+60928624
+25686087
+radix 17
+70912771
+69704402
+69358933
+64554822
+58820477
+61931012
+61985987
+26129087
+radix 18
+71231524
+71051252
+70966883
+62227667
+69575090
+63280736
+63297516
+26699407
+radix 19
+72743265
+71638726
+71595990
+62378229
+61170069
+64639168
+64361287
+27150427
+radix 20
+73544332
+73219218
+69908335
+62933335
+65249346
+65680945
+65650006
+27355150
+radix 21
+73704427
+73519719
+70395924
+63441542
+63940685
+72906696
+67058764
+27766841
+radix 22
+75433924
+74338906
+67871773
+64092473
+63565508
+66619708
+67094279
+28763924
+radix 23
+73850335
+69301782
+68368528
+64488785
+63024653
+68066056
+66847488
+28551783
+radix 24
+70204641
+70017694
+68737246
+64845718
+63541335
+66918926
+69254539
+29132129
+radix 25
+70855845
+70301783
+69537281
+64991486
+64441155
+65518746
+69378566
+29362760
+radix 26
+71640896
+70461614
+70154774
+65236955
+64792347
+65106858
+68281845
+29798072
+radix 27
+71552515
+71030799
+70959577
+65368358
+65244965
+65649571
+65944648
+29468067
+radix 28
+71962251
+71587113
+71715547
+65252620
+65591519
+66057948
+66957378
+28114849
+radix 29
+72491759
+72457349
+72335730
+64922366
+65489259
+66863734
+67087226
+28487426
+radix 30
+73411662
+72922686
+72917156
+64750239
+66035368
+67029068
+67666075
+28850587
+radix 31
+73970452
+73659060
+73152390
+64581272
+65701329
+68585956
+67311642
+29290105
+radix 32
+74485135
+74394511
+73420892
+64549058
+65141537
+68639239
+68711056
+29925749
+radix 33
+74926889
+74885711
+72847827
+64654882
+65104908
+69566120
+69322629
+27930453
+radix 34
+75281549
+76214857
+72254342
+64501263
+65445833
+68521664
+69218983
+30036608
+radix 35
+75808277
+75869094
+72102173
+64555847
+65319460
+67574813
+71497041
+28178381
+radix 36
+77635113
+75194087
+72176214
+64588163
+65418360
+67316650
+71241876
+30814244
+===*/
+
+function fastPathTest() {
+    var start = -256*256*256*256 + 1;
+    var end = 256*256*256*256 - 1;
+    var step = 115757;  // prime
+    var i;
+    var radix;
+    var tmp = [];
+
+    function flush() {
+        if (tmp.length > 0) {
+            // Note: here we're printing a checksum which is a small integer,
+            // so the checksum will go through the same fast path.
+            print(checkSumString(tmp.join(' ')));
+            tmp.length = 0;
+        }
+    }
+
+    function f(x) {
+        tmp.push(x);
+        if (tmp.length >= 10000) {
+            flush();
+        }
+    }
+
+    for (radix = 2; radix <= 36; radix++) {
+        print('radix', radix);
+        i = start;
+        for (;;) {
+            f(new Number(i).toString(radix));
+
+            if (i >= end) {
+                break;
+            }
+            i += step;
+            if (i >= end) {
+                i = end;  // always include end
+            }
+        }
+        flush();
+    }
+}
+
+try {
+    fastPathTest();
+} catch (e) {
+    print(e);
+}
+