diff --git a/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java b/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java
index 499297c64..83d9f256d 100644
--- a/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java
+++ b/spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/CustomRuntimeEventLoop.java
@@ -174,25 +174,33 @@ public final class CustomRuntimeEventLoop implements SmartLifecycle {
 
 	private FunctionInvocationWrapper locateFunction(Environment environment, FunctionCatalog functionCatalog, MediaType contentType) {
 		String handlerName = environment.getProperty("DEFAULT_HANDLER");
+		if (logger.isDebugEnabled()) {
+			logger.debug("Value of DEFAULT_HANDLER env: " + handlerName);
+		}
 		FunctionInvocationWrapper function = functionCatalog.lookup(handlerName, contentType.toString());
 		if (function == null) {
+			logger.debug("Could not locate function under DEFAULT_HANDLER");
 			handlerName = environment.getProperty("_HANDLER");
+			if (logger.isDebugEnabled()) {
+				logger.debug("Value of _HANDLER env: " + handlerName);
+			}
 			function = functionCatalog.lookup(handlerName, contentType.toString());
 		}
 
 		if (function == null) {
-			function = functionCatalog.lookup(null, contentType.toString());
+			logger.debug("Could not locate function under _HANDLER");
+			function = functionCatalog.lookup((String) null, contentType.toString());
 		}
 
 		if (function == null) {
+			logger.info("Could not determine default function");
 			handlerName = environment.getProperty("spring.cloud.function.definition");
+			if (logger.isDebugEnabled()) {
+				logger.debug("Value of 'spring.cloud.function.definition' env: " + handlerName);
+			}
 			function = functionCatalog.lookup(handlerName, contentType.toString());
 		}
 
-		if (function == null) {
-			function = functionCatalog.lookup(null, contentType.toString());
-		}
-
 		Assert.notNull(function, "Failed to locate function. Tried locating default function, "
 				+ "function by 'DEFAULT_HANDLER', '_HANDLER' env variable as well as'spring.cloud.function.definition'. "
 				+ "Functions available in catalog are: " + functionCatalog.getNames(null));