1 files changed, 17 insertions, 0 deletions

diff --git a/src/lread.c b/src/lread.c
index 9317933013e..ccc94c32dd1 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -2595,6 +2595,23 @@ read1 (readcharfun, pch, first_in_list)
                     break;
                   case 'N':
                     value = zero / zero;
+
+                    /* If that made a "negative" NaN, negate it.  */
+
+                    {
+                      int i;
+                      union { double d; char c[sizeof (double)]; } u_data, u_minus_zero;
+
+                      u_data.d = value;
+                      u_minus_zero.d = - 0.0;
+                      for (i = 0; i < sizeof (double); i++)
+                        if (u_data.c[i] & u_minus_zero.c[i])
+                          {
+                            value = - value;
+                            break;
+                          }
+                    }
+                    /* Now VALUE is a positive NaN.  */
                     break;
                   default:
                     value = atof (read_buffer + negative);