diff --git a/x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateEngine.java b/x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateEngine.java
index 7b87a9e87a542..d2159fd572f5d 100644
--- a/x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateEngine.java
+++ b/x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateEngine.java
@@ -35,6 +35,11 @@ public String render(TextTemplate textTemplate, Map<String, Object> model) {
         String mediaType = compileParams(detectContentType(template));
         template = trimContentType(textTemplate);
 
+        int indexStartMustacheExpression = template.indexOf("{{");
+        if (indexStartMustacheExpression == -1) {
+            return template;
+        }
+
         Map<String, Object> mergedModel = new HashMap<>();
         if (textTemplate.getParams() != null) {
             mergedModel.putAll(textTemplate.getParams());
diff --git a/x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateTests.java b/x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateTests.java
index 0e084af23e1fb..002d833c20913 100644
--- a/x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateTests.java
+++ b/x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/common/text/TextTemplateTests.java
@@ -21,6 +21,7 @@
 
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 
 import static java.util.Collections.singletonMap;
@@ -31,7 +32,10 @@
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.Matchers.nullValue;
+import static org.mockito.Matchers.any;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyZeroInteractions;
 import static org.mockito.Mockito.when;
 
 public class TextTemplateTests extends ESTestCase {
@@ -47,7 +51,7 @@ public void init() throws Exception {
     }
 
     public void testRender() throws Exception {
-        String templateText = "_template";
+        String templateText = "{{_template}}";
         Map<String, Object> params = singletonMap("param_key", "param_val");
         Map<String, Object> model = singletonMap("model_key", "model_val");
         Map<String, Object> merged = new HashMap<>(params);
@@ -72,7 +76,7 @@ public String execute() {
     }
 
     public void testRenderOverridingModel() throws Exception {
-        String templateText = "_template";
+        String templateText = "{{_template}}";
         Map<String, Object> params = singletonMap("key", "param_val");
         Map<String, Object> model = singletonMap("key", "model_val");
         ScriptType type = randomFrom(ScriptType.values());
@@ -94,7 +98,7 @@ public String execute() {
     }
 
     public void testRenderDefaults() throws Exception {
-        String templateText = "_template";
+        String templateText = "{{_template}}";
         Map<String, Object> model = singletonMap("key", "model_val");
 
         TemplateScript.Factory compiledTemplate = templateParams ->
@@ -113,6 +117,39 @@ public String execute() {
         assertThat(engine.render(template, model), is("rendered_text"));
     }
 
+    public void testDontInvokeScriptServiceOnNonMustacheText() {
+        assertNoCompilation("this is my text");
+        assertScriptServiceInvoked("}}{{");
+        assertScriptServiceInvoked("}}{{ctx.payload}}");
+    }
+
+    private void assertNoCompilation(String input) {
+        String output = engine.render(new TextTemplate(input), Collections.emptyMap());
+        assertThat(input, is(output));
+        verifyZeroInteractions(service);
+    }
+
+    private void assertScriptServiceInvoked(final String input) {
+        ScriptService scriptService = mock(ScriptService.class);
+        TextTemplateEngine e = new TextTemplateEngine(Settings.EMPTY, scriptService);
+
+        TemplateScript.Factory compiledTemplate = templateParams ->
+            new TemplateScript(templateParams) {
+                @Override
+                public String execute() {
+                    return input.toUpperCase(Locale.ROOT);
+                }
+            };
+
+        when(scriptService.compile(new Script(ScriptType.INLINE, lang, input,
+            Collections.singletonMap("content_type", "text/plain"), Collections.emptyMap()), Watcher.SCRIPT_TEMPLATE_CONTEXT))
+            .thenReturn(compiledTemplate);
+
+        String output = e.render(new TextTemplate(input), Collections.emptyMap());
+        verify(scriptService).compile(any(), any());
+        assertThat(output, is(input.toUpperCase(Locale.ROOT)));
+    }
+
     public void testParser() throws Exception {
         ScriptType type = randomScriptType();
         TextTemplate template =