diff --git a/.github/workflows/hooks-test.yml b/.github/workflows/hooks-test.yml
index a6a63f1..8582a10 100644
--- a/.github/workflows/hooks-test.yml
+++ b/.github/workflows/hooks-test.yml
@@ -1,6 +1,7 @@
 name: Test Plugin
 
 on:
+  workflow_dispatch:
   pull_request:
   push:
     branches: [main]
@@ -25,3 +26,5 @@ jobs:
         run: go run github.com/yuin/gopher-lua/cmd/glua@v1.1.1 tests/windows_test.lua
       - name: Test macOS OpenSSL selection
         run: bash tests/openssl_test.sh
+      - name: Test optional dependency diagnostics
+        run: bash tests/configure_options_test.sh
diff --git a/bin/install b/bin/install
index 84b400b..6d76372 100755
--- a/bin/install
+++ b/bin/install
@@ -233,13 +233,13 @@ os_based_configure_options() {
     if [ -n "$gmp_path" ]; then
       configure_options="--with-gmp=$gmp_path"
     else
-      echo "gmp not found, not including in installation"
+      echo "gmp not found, not including in installation" >&2
     fi
 
     if [ -n "$sodium_path" ]; then
       configure_options="$configure_options --with-sodium=$sodium_path"
     else
-      echo "sodium not found, not including in installation"
+      echo "sodium not found, not including in installation" >&2
     fi
 
     if [ -n "$freetype_path" ]; then
diff --git a/tests/configure_options_test.sh b/tests/configure_options_test.sh
new file mode 100644
index 0000000..061d0d5
--- /dev/null
+++ b/tests/configure_options_test.sh
@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+set -euo pipefail
+source bin/install
+
+# Optional dependency diagnostics must not become ./configure arguments.
+uname() { echo Darwin; }
+exit_if_homebrew_not_installed() { :; }
+homebrew_package_path() {
+  case "$1" in
+    gmp) [[ "$with_gmp" == yes ]] && echo /fake/gmp ;;
+    libsodium) [[ "$with_sodium" == yes ]] && echo /fake/libsodium ;;
+    *) echo "/fake/$1" ;;
+  esac
+  return 0
+}
+PHP_VERSION=8.4.10
+PHP_CONFIGURE_OPTIONS=
+diagnostics=$(mktemp)
+trap 'rm -f "$diagnostics"' EXIT
+for with_gmp in yes no; do
+  for with_sodium in yes no; do
+    options=$(construct_configure_options /fake/php 2>"$diagnostics")
+    [[ "$options" != *'not found'* ]] || {
+      echo 'Dependency diagnostics leaked into configure arguments' >&2
+      exit 1
+    }
+    [[ "$options" == *'--prefix=/fake/php'* ]]
+    if [[ "$with_gmp" == yes ]]; then
+      [[ "$options" == *'--with-gmp=/fake/gmp'* ]]
+    else
+      [[ "$options" != *'--with-gmp='* ]]
+      grep -q 'gmp not found' "$diagnostics"
+    fi
+    if [[ "$with_sodium" == yes ]]; then
+      [[ "$options" == *'--with-sodium=/fake/libsodium'* ]]
+    else
+      [[ "$options" != *'--with-sodium='* ]]
+      grep -q 'sodium not found' "$diagnostics"
+    fi
+  done
+done
+echo 'Optional dependency diagnostics and configure arguments passed'