diff --git a/lib/mes/ntoab.c b/lib/mes/ntoab.c
index a83b4d31..25780652 100644
--- a/lib/mes/ntoab.c
+++ b/lib/mes/ntoab.c
@@ -20,6 +20,10 @@
 
 #include <assert.h>
 #include <mes/lib.h>
+#include <stdint.h>
+
+#define STR(x) #x
+#define XSTR(s) STR(s)
 
 char *
 ntoab (long x, int base, int signed_p)
@@ -34,7 +38,26 @@ ntoab (long x, int base, int signed_p)
   if (signed_p && x < 0)
     {
       sign_p = 1;
-      u = -x;
+      if (x == LONG_MIN)
+        {
+           /* Cannot do u = (-x), so avoid it. */
+           long i;
+           if (base == 10)
+             return XSTR(LONG_MIN);
+           /* We cause the same result as
+                i = (-x) % base
+                u = (-x) / base
+              would in mathematics if x and base were integers.
+              It will be the case that -base < x <= 0 after the loop.
+              Because base > 1, the quotient will definitely fit into u.
+              i will contain the last digit to print. */
+           for (u = 0; x <= -base; x += base, ++u)
+             ;
+           i = -x;
+           *p-- = i > 9 ? 'a' + i - 10 : '0' + i;
+        }
+      else
+        u = -x;
     }
   else
     u = x;
diff --git a/lib/tests/scaffold/60-math.c b/lib/tests/scaffold/60-math.c
index 76e55092..24830e5b 100644
--- a/lib/tests/scaffold/60-math.c
+++ b/lib/tests/scaffold/60-math.c
@@ -196,6 +196,9 @@ ok1:
   if (strcmp ("-2147483648", itoa (i)))
     return 34;
 
+  if (strcmp ("-80000000", ntoab (i, 16, 1)))
+    return 35;
+
   oputs ("t: i = -2147483647\n");
   i = -2147483647;