diff --git a/doc/fixes36.1 b/doc/fixes36.1
index 8b53024cd..e95ecb7de 100644
--- a/doc/fixes36.1
+++ b/doc/fixes36.1
@@ -627,6 +627,8 @@ gas spore explosion killing a gas spore which triggers a recursive explosion
 	"You are hit by the gas spore's explosion!" (inner call, followed by)
 	"You are hit by the !" (outer call, possibly repeated for multiple
 	explosions causing multiple levels of recursion)
+if multiple bands of blank lines were squeezed out of DUMPLOG's map, spurious
+	blank lines appeared in the final map output
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/detect.c b/src/detect.c
index d835bd86d..7a6b6eb47 100644
--- a/src/detect.c
+++ b/src/detect.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	detect.c	$NHDT-Date: 1519281847 2018/02/22 06:44:07 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.80 $ */
+/* NetHack 3.6	detect.c	$NHDT-Date: 1522891623 2018/04/05 01:27:03 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.81 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1802,7 +1802,7 @@ int default_glyph, which_subset;
 void
 dump_map()
 {
-    int x, y, glyph, skippedrows;
+    int x, y, glyph, skippedrows, lastnonblank;
     int subset = TER_MAP | TER_TRP | TER_OBJ | TER_MON;
     int default_glyph = cmap_to_glyph(level.flags.arboreal ? S_tree : S_stone);
     char buf[BUFSZ];
@@ -1820,19 +1820,22 @@ dump_map()
     toprow = TRUE;
     for (y = 0; y < ROWNO; y++) {
         blankrow = TRUE; /* assume blank until we discover otherwise */
+        lastnonblank = -1; /* buf[] index rather than map's x */
         for (x = 1; x < COLNO; x++) {
             int ch, color;
             unsigned special;
 
-            glyph = reveal_terrain_getglyph(x,y, FALSE, u.uswallow,
+            glyph = reveal_terrain_getglyph(x, y, FALSE, u.uswallow,
                                             default_glyph, subset);
             (void) mapglyph(glyph, &ch, &color, &special, x, y);
             buf[x - 1] = ch;
-            if (ch != ' ')
+            if (ch != ' ') {
                 blankrow = FALSE;
+                lastnonblank = x - 1;
+            }
         }
         if (!blankrow) {
-            buf[x - 2] = '\0';
+            buf[lastnonblank + 1] = '\0';
             if (toprow) {
                 skippedrows = 0;
                 toprow = FALSE;
@@ -1840,6 +1843,7 @@ dump_map()
             for (x = 0; x < skippedrows; x++)
                 putstr(0, 0, "");
             putstr(0, 0, buf); /* map row #y */
+            skippedrows = 0;
         } else {
             ++skippedrows;
         }