diff --git a/README.md b/README.md
index d25714a..c1af4ff 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,23 @@ GitHub Action and Docker image used to deploy a Docker stack on a Docker Swarm.
 | `debug` | `DEBUG` | Verbose logging | | **0** |
 | `scale_after` | `SCALE_AFTER` | Scale a service after a deployment has converged successfully. Example: servicename=1 | | |
 
+### A note on whitespace
+
+`registry`, `username`, `remote_host`, `remote_port` and `remote_user` cannot
+contain whitespace, so any is removed before the value is used, and a line
+naming the input is written to the log when that happens:
+
+```
+Input remote_host: removed whitespace from the value
+```
+
+This exists because a stray newline in a GitHub secret is invisible in the
+repository UI, and used to surface much later as an opaque
+`ssh: Could not resolve hostname`.
+
+`remote_private_key` and `password` are left exactly as given — newlines are
+structural in a PEM key, and whitespace can be a legitimate part of a token.
+
 
 ## Using the GitHub Action
 
diff --git a/news/1.bugfix b/news/1.bugfix
new file mode 100644
index 0000000..28e599d
--- /dev/null
+++ b/news/1.bugfix
@@ -0,0 +1 @@
+Fixed a stray newline or space in `remote_host` (or `registry`, `username`, `remote_port`, `remote_user`) breaking the deploy with an opaque `ssh: Could not resolve hostname`. Whitespace is now removed from those inputs, and the log says when it was. @ericof
diff --git a/scripts/docker-entrypoint.sh b/scripts/docker-entrypoint.sh
index 12b42e7..1400f3d 100755
--- a/scripts/docker-entrypoint.sh
+++ b/scripts/docker-entrypoint.sh
@@ -10,6 +10,29 @@ ENV_FILE_PATH="/root/.env"
 OPTS=("--with-registry-auth" "--resolve-image=${RESOLVE_IMAGE:-always}")
 [ "${PRUNE:-0}" = "1" ] && OPTS+=("--prune")
 
+# Inputs whose values cannot legally contain whitespace. A newline pasted into
+# a GitHub secret is invisible in the repository UI and only surfaces much
+# later, as an opaque `ssh: Could not resolve hostname`, so strip it here.
+#
+# REMOTE_PRIVATE_KEY and PASSWORD are deliberately NOT in this list, and must
+# not be added: newlines are structural in a PEM key, and whitespace can be a
+# legitimate part of a registry token.
+TRIMMED_INPUTS=(REGISTRY USERNAME REMOTE_HOST REMOTE_PORT REMOTE_USER)
+
+
+trim_inputs() {
+  local name original trimmed
+  for name in "${TRIMMED_INPUTS[@]}"; do
+    original="${!name-}"
+    trimmed="${original//[[:space:]]/}"
+    if [ "${trimmed}" != "${original}" ]; then
+      # Reported unconditionally, not only under DEBUG: the whole problem with
+      # this class of mistake is that it is invisible everywhere else.
+      echo "Input ${name,,}: removed whitespace from the value"
+      export "${name}=${trimmed}"
+    fi
+  done
+}
 
 login() {
   echo "${PASSWORD}" | docker login "${REGISTRY}" -u "${USERNAME}" --password-stdin
@@ -127,6 +150,12 @@ else
   SSH_VERBOSE=""
 fi
 
+# NORMALISE INPUTS
+# Runs before the first use of any of them, and before the required-input
+# checks below, so an input that is nothing but whitespace is reported as
+# missing rather than being passed on to ssh.
+trim_inputs
+
 # PROCEED WITH LOGIN
 if [ -z "${USERNAME}" ] || [ -z "${PASSWORD}" ]; then
   echo "Container Registry: No authentication provided"
diff --git a/tests/entrypoint.bats b/tests/entrypoint.bats
index cce23e6..a800341 100644
--- a/tests/entrypoint.bats
+++ b/tests/entrypoint.bats
@@ -80,6 +80,115 @@ run_entrypoint() {
   [[ "$output" == *"Input stack_name is required!"* ]]
 }
 
+# --- input whitespace (issue #1) ----------------------------------------------
+
+# Source the script, run trim_inputs against a controlled environment, and
+# print the resulting value of one variable.
+#
+# The value is printed inside brackets on purpose: bats strips trailing
+# newlines from $output, so an untrimmed `host\n` would compare equal to `host`
+# and the assertion would pass whether the trimming happened or not.
+trim_and_print() {
+  local var="$1"
+  shift
+  run env -i PATH="${PATH}" HOME="${BATS_TEST_TMPDIR}" WANT="${var}" "$@" \
+    bash -c "
+      source '${ENTRYPOINT}'
+      trim_inputs >/dev/null
+      printf '[%s]' \"\${!WANT}\"
+    "
+}
+
+@test "remote_host loses a trailing newline (issue #1)" {
+  trim_and_print REMOTE_HOST REMOTE_HOST=$'swarm.example.com\n'
+  [ "$status" -eq 0 ]
+  [ "$output" = "[swarm.example.com]" ]
+}
+
+@test "remote_host loses whitespace in the middle of the value (issue #1)" {
+  trim_and_print REMOTE_HOST REMOTE_HOST='swarm .example.com'
+  [ "$status" -eq 0 ]
+  [ "$output" = "[swarm.example.com]" ]
+}
+
+@test "remote_user is trimmed (issue #1)" {
+  trim_and_print REMOTE_USER REMOTE_USER=$'deploy\n'
+  [ "$status" -eq 0 ]
+  [ "$output" = "[deploy]" ]
+}
+
+@test "remote_port is trimmed (issue #1)" {
+  trim_and_print REMOTE_PORT REMOTE_PORT=$' 2222\n'
+  [ "$status" -eq 0 ]
+  [ "$output" = "[2222]" ]
+}
+
+@test "registry is trimmed (issue #1)" {
+  trim_and_print REGISTRY REGISTRY=$'ghcr.io\n'
+  [ "$status" -eq 0 ]
+  [ "$output" = "[ghcr.io]" ]
+}
+
+@test "username is trimmed (issue #1)" {
+  trim_and_print USERNAME USERNAME=$'someone\n'
+  [ "$status" -eq 0 ]
+  [ "$output" = "[someone]" ]
+}
+
+@test "trimming an input is reported on stdout (issue #1)" {
+  # The point of the issue: the mistake is invisible everywhere else, so the
+  # fix has to be visible without DEBUG.
+  run env -i PATH="${PATH}" HOME="${BATS_TEST_TMPDIR}" \
+    REMOTE_HOST=$'swarm.example.com\n' \
+    bash -c "source '${ENTRYPOINT}'; trim_inputs"
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"Input remote_host: removed whitespace from the value"* ]]
+}
+
+@test "a clean input is left alone and reported silently (issue #1)" {
+  run env -i PATH="${PATH}" HOME="${BATS_TEST_TMPDIR}" \
+    REMOTE_HOST=swarm.example.com REMOTE_USER=deploy REMOTE_PORT=22 \
+    bash -c "source '${ENTRYPOINT}'; trim_inputs"
+  [ "$status" -eq 0 ]
+  [ -z "$output" ]
+}
+
+@test "remote_private_key is never trimmed (issue #1)" {
+  # Newlines are structural in a PEM key. Counting them is what makes a
+  # regression here fail loudly instead of silently mangling the key.
+  run env -i PATH="${PATH}" HOME="${BATS_TEST_TMPDIR}" \
+    REMOTE_PRIVATE_KEY=$'-----BEGIN-----\nabc\n-----END-----\n' \
+    bash -c "
+      source '${ENTRYPOINT}'
+      trim_inputs >/dev/null
+      printf '%s' \"\${REMOTE_PRIVATE_KEY}\" | wc -l
+    "
+  [ "$status" -eq 0 ]
+  [ "${output// /}" = "3" ]
+}
+
+@test "password is never trimmed (issue #1)" {
+  trim_and_print PASSWORD PASSWORD='tok en '
+  [ "$status" -eq 0 ]
+  [ "$output" = "[tok en ]" ]
+}
+
+@test "the trim runs as part of the deploy flow (issue #1)" {
+  # Every other test in this section calls trim_inputs directly; this one is
+  # what proves it is actually wired into the script's flow, and that it runs
+  # before the required-input checks.
+  run_entrypoint REMOTE_HOST=$'swarm.example.com\n'
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"Input remote_host: removed whitespace from the value"* ]]
+  [[ "$output" == *"Input remote_user is required!"* ]]
+}
+
+@test "a remote_host of only whitespace is reported as missing (issue #1)" {
+  run_entrypoint REMOTE_HOST=$'  \n'
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"Input remote_host is required!"* ]]
+}
+
 # --- container registry login -------------------------------------------------
 
 @test "skips login when no credentials are given (issue #4)" {