diff --git a/regressions/rhbz557655-expected.out b/regressions/rhbz557655-expected.out
deleted file mode 100644
index 7d37e84..0000000
--- a/regressions/rhbz557655-expected.out
+++ /dev/null
@@ -1,22 +0,0 @@
-0
-16
-8
--1073741824
-1073741823
-set-memsize: memsize: integer out of range
-set-memsize: memsize: integer out of range
-set-memsize: memsize: integer out of range
-set-memsize: memsize: integer out of range
-set-memsize: memsize: invalid integer parameter (xstrtol returned 4)
-set-memsize: memsize: invalid integer parameter (xstrtol returned 2)
-set-memsize: memsize: invalid integer parameter (xstrtol returned 2)
-set-memsize: memsize: invalid integer parameter (xstrtol returned 2)
-1234
-1234
-1234
-libguestfs: error: truncate_size: ftruncate: /test: File too large
-truncate-size: size: invalid integer parameter (xstrtoll returned 1)
-truncate-size: size: invalid integer parameter (xstrtoll returned 4)
-truncate-size: size: invalid integer parameter (xstrtoll returned 2)
-truncate-size: size: invalid integer parameter (xstrtoll returned 2)
-truncate-size: size: invalid integer parameter (xstrtoll returned 2)
diff --git a/regressions/rhbz557655-expected.stderr b/regressions/rhbz557655-expected.stderr
new file mode 100644
index 0000000..ea560e8
--- /dev/null
+++ b/regressions/rhbz557655-expected.stderr
@@ -0,0 +1,14 @@
+set-memsize: memsize: integer out of range
+set-memsize: memsize: integer out of range
+set-memsize: memsize: integer out of range
+set-memsize: memsize: integer out of range
+set-memsize: memsize: invalid integer parameter (xstrtol returned 4)
+set-memsize: memsize: invalid integer parameter (xstrtol returned 2)
+set-memsize: memsize: invalid integer parameter (xstrtol returned 2)
+set-memsize: memsize: invalid integer parameter (xstrtol returned 2)
+libguestfs: error: truncate_size: ftruncate: /test: File too large
+truncate-size: size: invalid integer parameter (xstrtoll returned 1)
+truncate-size: size: invalid integer parameter (xstrtoll returned 4)
+truncate-size: size: invalid integer parameter (xstrtoll returned 2)
+truncate-size: size: invalid integer parameter (xstrtoll returned 2)
+truncate-size: size: invalid integer parameter (xstrtoll returned 2)
diff --git a/regressions/rhbz557655-expected.stdout b/regressions/rhbz557655-expected.stdout
new file mode 100644
index 0000000..80bc8bc
--- /dev/null
+++ b/regressions/rhbz557655-expected.stdout
@@ -0,0 +1,8 @@
+0
+16
+8
+-1073741824
+1073741823
+1234
+1234
+1234
diff --git a/regressions/rhbz557655.sh b/regressions/rhbz557655.sh
index 6ef0b70..85cfb1e 100755
--- a/regressions/rhbz557655.sh
+++ b/regressions/rhbz557655.sh
@@ -21,10 +21,10 @@
 # "guestfish number parsing should not use atoi, should support '0...' for octal and '0x...' for hexadecimal"
 
 set -e
-rm -f test.out
+rm -f test.out test.err
 export LANG=C
 
-../fish/guestfish >> test.out 2>&1 <<EOF
+../fish/guestfish >> test.out 2>> test.err <<EOF
 # set-memsize is just a convenient non-daemon function that
 # takes a single integer argument.
 set-memsize 0
@@ -49,7 +49,7 @@ get-memsize
 -set-memsize 123L
 EOF
 
-../fish/guestfish >> test.out 2>&1 <<EOF
+../fish/guestfish >> test.out 2>> test.err <<EOF
 alloc test1.img 10M
 run
 part-disk /dev/sda mbr
@@ -79,5 +79,15 @@ filesize /test
 -truncate-size /test 123L
 EOF
 
-diff -u test.out rhbz557655-expected.out
-rm test.out test1.img
+# If we are running with debugging enabled (or even if not), then
+# other messages and warnings can end up in the test.err (stderr) log.
+# Thus filter out only lines we expect.  'proc 200' is the procedure
+# number of truncate_size.
+mv test.err test.err~
+grep -E 'set[-_]memsize|truncate[-_]size' test.err~ |
+  grep -Ev 'proc 200' > test.err
+rm test.err~
+
+diff -u test.out rhbz557655-expected.stdout
+diff -u test.err rhbz557655-expected.stderr
+rm test.out test.err test1.img