diff --git a/compose/asc-globals.c b/compose/asc-globals.c
index 938e27ff..4330bd6f 100644
--- a/compose/asc-globals.c
+++ b/compose/asc-globals.c
@@ -190,6 +190,11 @@ void
 asc_globals_set_use_optipng (gboolean enabled)
 {
 	AscGlobalsPrivate *priv = asc_globals_get_priv ();
+	if (enabled && priv->optipng_bin == NULL) {
+		g_critical ("Refusing to enable optipng: not found in $PATH");
+		priv->use_optipng = FALSE;
+		return;
+	}
 	priv->use_optipng = enabled;
 }
 
@@ -216,6 +221,8 @@ asc_globals_set_optipng_binary (const gchar *path)
 	AscGlobalsPrivate *priv = asc_globals_get_priv ();
 	g_free (priv->optipng_bin);
 	priv->optipng_bin = g_strdup (path);
+	if (priv->optipng_bin == NULL)
+		priv->use_optipng = FALSE;
 }
 
 /**
diff --git a/compose/asc-image.c b/compose/asc-image.c
index 9102fd8d..5d657ef6 100644
--- a/compose/asc-image.c
+++ b/compose/asc-image.c
@@ -204,6 +204,7 @@ asc_optimize_png (const gchar *fname, GError **error)
 {
 	gint exit_status;
 	gboolean r;
+	const gchar *optipng_path;
 	g_autofree gchar *opng_stdout = NULL;
 	g_autofree gchar *opng_stderr = NULL;
 	g_autofree const gchar **argv = NULL;
@@ -212,8 +213,17 @@ asc_optimize_png (const gchar *fname, GError **error)
 	if (!asc_globals_get_use_optipng ())
 		return TRUE;
 
+	optipng_path = asc_globals_get_optipng_binary ();
+	if (optipng_path == NULL) {
+		g_set_error (error,
+			     ASC_IMAGE_ERROR,
+			     ASC_IMAGE_ERROR_FAILED,
+			     "optipng not found in $PATH");
+		return FALSE;
+	}
+
 	argv = g_new0 (const gchar*, 2 + 1);
-	argv[0] = asc_globals_get_optipng_binary ();
+	argv[0] = optipng_path;
 	argv[1] = fname;
 
 	/* NOTE: Maybe add an option to run optipng with stronger optimization? (>= -o4) */
diff --git a/tests/test-compose.c b/tests/test-compose.c
index 31334ea0..f1afb4e2 100644
--- a/tests/test-compose.c
+++ b/tests/test-compose.c
@@ -27,6 +27,11 @@
 
 static gchar *datadir = NULL;
 
+typedef struct
+{
+	gchar *path;
+} Fixture;
+
 /**
  * test_utils:
  *
@@ -493,6 +498,32 @@ test_compose_desktop_entry ()
 	g_clear_pointer (&cpt, g_object_unref);
 }
 
+static void
+setup (Fixture *fixture, gconstpointer user_data)
+{
+	fixture->path = g_strdup (g_getenv ("PATH"));
+	/* not unset because glib has a hardcoded fallback */
+	g_setenv ("PATH", "", TRUE);
+}
+
+static void
+teardown (Fixture *fixture, gconstpointer user_data)
+{
+	g_setenv ("PATH", fixture->path, TRUE);
+	g_clear_pointer (&fixture->path, g_free);
+}
+
+static void
+test_compose_optipng_not_found (Fixture *fixture, gconstpointer user_data)
+{
+	g_test_expect_message (G_LOG_DOMAIN,
+			       G_LOG_LEVEL_CRITICAL,
+			       "*Refusing to enable optipng: not found in $PATH");
+	asc_globals_set_use_optipng (TRUE);
+	g_assert_false (asc_globals_get_use_optipng ());
+	g_test_assert_expected_messages ();
+}
+
 int
 main (int argc, char **argv)
 {
@@ -513,6 +544,7 @@ main (int argc, char **argv)
 	/* only critical and error are fatal */
 	g_log_set_fatal_mask (NULL, G_LOG_LEVEL_ERROR | G_LOG_LEVEL_CRITICAL);
 
+	g_test_add ("/AppStream/Compose/OptipngNotfound", Fixture, NULL, setup, test_compose_optipng_not_found, teardown);
 	g_test_add_func ("/AppStream/Compose/Utils", test_utils);
 	g_test_add_func ("/AppStream/Compose/FontInfo", test_read_fontinfo);
 	g_test_add_func ("/AppStream/Compose/Image", test_image_transform);