diff --git a/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java b/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java
index 3caad594814..f7c34631107 100755
--- a/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java
+++ b/spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java
@@ -121,7 +121,7 @@ public class DevToolsPropertyDefaultsPostProcessor implements EnvironmentPostPro
 
 	private boolean isWebApplication(Environment environment) {
 		for (String candidate : WEB_ENVIRONMENT_CLASSES) {
-			Class<?> environmentClass = ClassUtils.resolveClassName(candidate,
+			Class<?> environmentClass = resolveClassName(candidate,
 					environment.getClass().getClassLoader());
 			if (environmentClass != null && environmentClass.isInstance(environment)) {
 				return true;
@@ -130,4 +130,13 @@ public class DevToolsPropertyDefaultsPostProcessor implements EnvironmentPostPro
 		return false;
 	}
 
+	private Class<?> resolveClassName(String candidate, ClassLoader classLoader) {
+		try {
+			return ClassUtils.resolveClassName(candidate, classLoader);
+		}
+		catch (IllegalArgumentException ex) {
+			return null;
+		}
+	}
+
 }