diff --git a/ANNOUNCE b/ANNOUNCE
index 7386894cf..abc870d72 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -299,6 +299,7 @@ Version 1.6.0beta17 [March 10, 2012]
     header.
 
 Version 1.6.0beta18 [March 10, 2012]
+  Issue a png_benign_error() instead of png_warning() about bad palette index.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index ae1d58c60..2fe5123d7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4050,6 +4050,7 @@ Version 1.6.0beta17 [March 10, 2012]
     header.
 
 Version 1.6.0beta18 [March 10, 2012]
+  Issue a png_benign_error() instead of png_warning() about bad palette index.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/libpng-manual.txt b/libpng-manual.txt
index ff13702c5..b7832e3e8 100644
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -4521,7 +4521,8 @@ From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
 function) incorrectly returned a value of type png_uint_32.
 
 Checking for invalid palette index on read or write was added at libpng
-1.5.10.  This is enabled by default but can be disabled in each png_ptr with
+1.5.10.  When an invalid index is found, libpng issues a benign error.
+This is enabled by default but can be disabled in each png_ptr with
 
    png_set_check_for_invalid_index(png_ptr, allowed);
 
diff --git a/libpng.3 b/libpng.3
index 489a12d01..6aa3def28 100644
--- a/libpng.3
+++ b/libpng.3
@@ -5529,7 +5529,8 @@ From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
 function) incorrectly returned a value of type png_uint_32.
 
 Checking for invalid palette index on read or write was added at libpng
-1.5.10.  This is enabled by default but can be disabled in each png_ptr with
+1.5.10.  When an invalid index is found, libpng issues a benign error.
+This is enabled by default but can be disabled in each png_ptr with
 
    png_set_check_for_invalid_index(png_ptr, allowed);
 
diff --git a/pngread.c b/pngread.c
index 68304b8b4..36e02d5ee 100644
--- a/pngread.c
+++ b/pngread.c
@@ -669,7 +669,7 @@ png_read_end(png_structrp png_ptr, png_inforp info_ptr)
    /* Report invalid palette index; added at libng-1.5.10 */
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
       png_ptr->num_palette_max > png_ptr->num_palette)
-     png_warning(png_ptr, "Read palette index exceeding num_palette");
+     png_benign_error(png_ptr, "Read palette index exceeding num_palette");
 #endif
 
    do
diff --git a/pngset.c b/pngset.c
index 882be9718..07b78c4fa 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1343,7 +1343,7 @@ png_set_check_for_invalid_index(png_structrp png_ptr, int allowed)
 {
    png_debug(1, "in png_set_check_for_invalid_index");
 
-   if (allowed)
+   if (allowed > 0)
       png_ptr->num_palette_max = 0;
 
    else
diff --git a/pngwrite.c b/pngwrite.c
index 4b10b0417..7f213c9a6 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -310,7 +310,7 @@ png_write_end(png_structrp png_ptr, png_inforp info_ptr)
 
 #ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
    if (png_ptr->num_palette_max > png_ptr->num_palette)
-      png_warning(png_ptr, "Wrote palette index exceeding num_palette");
+      png_benign_error(png_ptr, "Wrote palette index exceeding num_palette");
 #endif
 
    /* See if user wants us to write information chunks */