diff --git a/bin/pt-mysql-summary b/bin/pt-mysql-summary
index 799d4463..17cff681 100755
--- a/bin/pt-mysql-summary
+++ b/bin/pt-mysql-summary
@@ -793,22 +793,21 @@ find_my_cnf_file() {
    local port="${2:-""}"
 
    local cnf_file=""
-   if test -n "$port" && grep -- "/mysqld.*--port=$port" "${file}" >/dev/null 2>&1 ; then
-      cnf_file="$(grep -- "/mysqld.*--port=$port" "${file}" \
-         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }' \
-         | head -n1)"
+
+   if [ "$port" ]; then
+      cnf_file="$(grep --max-count 1 "/mysqld.*--port=$port" "$file" \
+         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }')"
    else
-      cnf_file="$(grep '/mysqld' "${file}" \
-         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }' \
-         | head -n1)"
+      cnf_file="$(grep --max-count 1 '/mysqld' "$file" \
+         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }')"
    fi
 
-   if [ ! -n "${cnf_file}" ]; then
-      cnf_file="/etc/my.cnf";
-      if [ ! -e "${cnf_file}" ]; then
-         cnf_file="/etc/mysql/my.cnf";
-      fi
-      if [ ! -e "${cnf_file}" ]; then
+   if [ -z "$cnf_file" ]; then
+      if [ -e "/etc/my.cnf" ]; then
+         cnf_file="/etc/my.cnf"
+      elif [ -e "/etc/mysql/my.cnf" ]; then
+         cnf_file="/etc/mysql/my.cnf"
+      elif [ -e "/var/db/mysql/my.cnf" ]; then
          cnf_file="/var/db/mysql/my.cnf";
       fi
    fi
diff --git a/lib/bash/collect_mysql_info.sh b/lib/bash/collect_mysql_info.sh
index f4dd7337..ff79deb6 100644
--- a/lib/bash/collect_mysql_info.sh
+++ b/lib/bash/collect_mysql_info.sh
@@ -60,23 +60,24 @@ find_my_cnf_file() {
    local port="${2:-""}"
 
    local cnf_file=""
-   if test -n "$port" && grep -- "/mysqld.*--port=$port" "${file}" >/dev/null 2>&1 ; then
-      cnf_file="$(grep -- "/mysqld.*--port=$port" "${file}" \
-         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }' \
-         | head -n1)"
+
+   if [ "$port" ]; then
+      # Find the cnf file for the specific port.
+      cnf_file="$(grep --max-count 1 "/mysqld.*--port=$port" "$file" \
+         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }')"
    else
-      cnf_file="$(grep '/mysqld' "${file}" \
-         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }' \
-         | head -n1)"
+      # Find the cnf file for the first mysqld instance.
+      cnf_file="$(grep --max-count 1 '/mysqld' "$file" \
+         | awk 'BEGIN{RS=" "; FS="=";} $1 ~ /--defaults-file/ { print $2; }')"
    fi
 
-   if [ ! -n "${cnf_file}" ]; then
-      # "Cannot autodetect config file, trying common locations"
-      cnf_file="/etc/my.cnf";
-      if [ ! -e "${cnf_file}" ]; then
-         cnf_file="/etc/mysql/my.cnf";
-      fi
-      if [ ! -e "${cnf_file}" ]; then
+   if [ -z "$cnf_file" ]; then
+      # Cannot autodetect config file, try common locations.
+      if [ -e "/etc/my.cnf" ]; then
+         cnf_file="/etc/my.cnf"
+      elif [ -e "/etc/mysql/my.cnf" ]; then
+         cnf_file="/etc/mysql/my.cnf"
+      elif [ -e "/var/db/mysql/my.cnf" ]; then
          cnf_file="/var/db/mysql/my.cnf";
       fi
    fi
diff --git a/t/lib/bash/collect_mysql_info.sh b/t/lib/bash/collect_mysql_info.sh
index 6bdfc5c2..c2226d6f 100644
--- a/t/lib/bash/collect_mysql_info.sh
+++ b/t/lib/bash/collect_mysql_info.sh
@@ -79,26 +79,50 @@ is \
    "collect_internal_vars works"
 
 # find_my_cnf_file
+
+# We know the port is 12345 (2nd to last test), but the sandbox is started
+# with just --defaults-file, no --port, so find_my_cnf_file isn't going to
+# be able to get the specific cnf file, and the test machine shouldn't have
+# any of the default files (/etc/my.cnf, etc.).
 cnf_file=$(find_my_cnf_file "$p/mysqld-instances" ${port});
 
-is \
-   "$cnf_file" \
-   "/tmp/12345/my.sandbox.cnf" \
-   "find_my_cnf_file gets the correct file"
+is "$cnf_file" "" "find_my_cnf_file gets the correct file"
 [ $? -ne 0 ] && diag "$p/mysqld-instances"
 
+# ps-mysqld-001.txt has several instances:
+# port 3306  cnf -
+# port 12345 cnf /tmp/12345/my.sandbox.cnf
+# port 12346 cnf /tmp/12346/my.sandbox.cnf
+
 res=$(find_my_cnf_file "$samples/ps-mysqld-001.txt")
-is "$res" "/tmp/12345/my.sandbox.cnf" "ps-mysqld-001.txt"
+is "$res" "" "ps-mysqld-001.txt no port"
+
+res=$(find_my_cnf_file "$samples/ps-mysqld-001.txt" 3306)
+is "$res" "" "ps-mysqld-001.txt port but no cnf"
+
+res=$(find_my_cnf_file "$samples/ps-mysqld-001.txt" 999)
+is "$res" "" "ps-mysqld-001.txt nonexistent port"
 
 res=$(find_my_cnf_file "$samples/ps-mysqld-001.txt" 12346)
-is "$res" "/tmp/12346/my.sandbox.cnf" "ps-mysqld-001.txt with port"
+is "$res" "/tmp/12346/my.sandbox.cnf" "ps-mysqld-001.txt port 12346"
+
+res=$(find_my_cnf_file "$samples/ps-mysqld-001.txt" 12345)
+is "$res" "/tmp/12345/my.sandbox.cnf" "ps-mysqld-001.txt port 12345"
+
+# ps-mysqld-004.txt has 1 instance without --port using
+# --defaults-file=/var/lib/mysql/my.cnf
 
 res=$(find_my_cnf_file "$samples/ps-mysqld-004.txt")
-is "$res" "/var/lib/mysql/my.cnf" "ps-mysqld-004.txt"
+is "$res" "/var/lib/mysql/my.cnf" "ps-mysqld-004.txt no port"
 
 res=$(find_my_cnf_file "$samples/ps-mysqld-004.txt" 12345)
-is "$res" "/var/lib/mysql/my.cnf" "ps-mysqld-004.txt with port"
+is "$res" "" "ps-mysqld-004.txt port 12345"
 
+# ps-mysqld-005.txt has the 3 sandbox instances, but 12347
+# is first, which was causing bug 1070916.
+
+res=$(find_my_cnf_file "$samples/ps-mysqld-005.txt" 12345)
+is "$res" "" "ps-mysqld-005.txt port 12345 (bug 1070916)"
 
 # collect_mysql_databases
 $CMD_MYSQL $EXT_ARGV -ss -e 'SHOW DATABASES' > "$PT_TMPDIR/mysql_collect_databases" 2>/dev/null
diff --git a/t/pt-mysql-summary/samples/ps-mysqld-005.txt b/t/pt-mysql-summary/samples/ps-mysqld-005.txt
new file mode 100644
index 00000000..2f41faf5
--- /dev/null
+++ b/t/pt-mysql-summary/samples/ps-mysqld-005.txt
@@ -0,0 +1,4 @@
+   PID TTY      STAT   TIME COMMAND
+  1427 ?        Sl     0:13 /home/jenkins/mysql-bin/mysql-5.5.24-i386-barebones/bin/mysqld --defaults-file=/tmp/12347/my.sandbox.cnf
+ 20928 ?        Sl     0:07 /home/jenkins/mysql-bin/mysql-5.5.24-i386-barebones/bin/mysqld --defaults-file=/tmp/12345/my.sandbox.cnf
+ 29930 ?        Sl     0:00 /home/jenkins/mysql-bin/mysql-5.5.24-i386-barebones/bin/mysqld --defaults-file=/tmp/12346/my.sandbox.cnf