diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/BeanTypeRegistry.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/BeanTypeRegistry.java
index 4e9c176994..d013cc55bd 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/BeanTypeRegistry.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/BeanTypeRegistry.java
@@ -77,7 +77,7 @@ final class BeanTypeRegistry implements SmartInitializingSingleton {
 
 	private final Map<String, Class<?>> beanTypes = new HashMap<>();
 
-	private int lastBeanDefinitionCount = 0;
+	private final Map<String, RootBeanDefinition> beanDefinitions = new HashMap<>();
 
 	private BeanTypeRegistry(DefaultListableBeanFactory beanFactory) {
 		this.beanFactory = beanFactory;
@@ -142,7 +142,7 @@ final class BeanTypeRegistry implements SmartInitializingSingleton {
 	public void afterSingletonsInstantiated() {
 		// We're done at this point, free up some memory
 		this.beanTypes.clear();
-		this.lastBeanDefinitionCount = 0;
+		this.beanDefinitions.clear();
 	}
 
 	private void addBeanType(String name) {
@@ -155,9 +155,22 @@ final class BeanTypeRegistry implements SmartInitializingSingleton {
 	}
 
 	private void addBeanTypeForNonAliasDefinition(String name) {
+		addBeanTypeForNonAliasDefinition(name, getBeanDefinition(name));
+	}
+
+	private RootBeanDefinition getBeanDefinition(String name) {
+		try {
+			return (RootBeanDefinition) this.beanFactory.getMergedBeanDefinition(name);
+		}
+		catch (BeanDefinitionStoreException ex) {
+			logIgnoredError("unresolvable metadata in bean definition", name, ex);
+			return null;
+		}
+	}
+
+	private void addBeanTypeForNonAliasDefinition(String name,
+			RootBeanDefinition beanDefinition) {
 		try {
-			RootBeanDefinition beanDefinition = (RootBeanDefinition) this.beanFactory
-					.getMergedBeanDefinition(name);
 			if (!beanDefinition.isAbstract()
 					&& !requiresEagerInit(beanDefinition.getFactoryBeanName())) {
 				String factoryName = BeanFactory.FACTORY_BEAN_PREFIX + name;
@@ -172,15 +185,12 @@ final class BeanTypeRegistry implements SmartInitializingSingleton {
 					this.beanTypes.put(name, this.beanFactory.getType(name));
 				}
 			}
+			this.beanDefinitions.put(name, beanDefinition);
 		}
 		catch (CannotLoadBeanClassException ex) {
 			// Probably contains a placeholder
 			logIgnoredError("bean class loading failure for bean", name, ex);
 		}
-		catch (BeanDefinitionStoreException ex) {
-			// Probably contains a placeholder
-			logIgnoredError("unresolvable metadata in bean definition", name, ex);
-		}
 	}
 
 	private void logIgnoredError(String message, String name, Exception ex) {
@@ -195,15 +205,24 @@ final class BeanTypeRegistry implements SmartInitializingSingleton {
 	}
 
 	private void updateTypesIfNecessary() {
-		if (this.lastBeanDefinitionCount != this.beanFactory.getBeanDefinitionCount()) {
-			Iterator<String> names = this.beanFactory.getBeanNamesIterator();
-			while (names.hasNext()) {
-				String name = names.next();
-				if (!this.beanTypes.containsKey(name)) {
-					addBeanType(name);
+		Iterator<String> names = this.beanFactory.getBeanNamesIterator();
+		while (names.hasNext()) {
+			String name = names.next();
+			if (!this.beanTypes.containsKey(name)) {
+				addBeanType(name);
+			}
+			else {
+				if (!this.beanFactory.isAlias(name)
+						&& !this.beanFactory.containsSingleton(name)) {
+					RootBeanDefinition beanDefinition = getBeanDefinition(name);
+					RootBeanDefinition existingDefinition = this.beanDefinitions.put(name,
+							beanDefinition);
+					if (existingDefinition != null
+							&& !beanDefinition.equals(existingDefinition)) {
+						addBeanTypeForNonAliasDefinition(name, beanDefinition);
+					}
 				}
 			}
-			this.lastBeanDefinitionCount = this.beanFactory.getBeanDefinitionCount();
 		}
 	}
 
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnBeanTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnBeanTests.java
index 546b5f4836..5d6cfcc1ab 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnBeanTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnBeanTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -137,6 +137,16 @@ public class ConditionalOnBeanTests {
 		assertThat(context.getBean("bar")).isEqualTo("bar");
 	}
 
+	@Test
+	public void conditionEvaluationConsidersChangeInTypeWhenBeanIsOverridden() {
+		this.context.register(OriginalDefinition.class, OverridingDefinition.class,
+				ConsumingConfiguration.class);
+		this.context.refresh();
+		assertThat(this.context.containsBean("testBean")).isTrue();
+		assertThat(this.context.getBean(Integer.class)).isEqualTo(1);
+		assertThat(this.context.getBeansOfType(ConsumingConfiguration.class)).isEmpty();
+	}
+
 	@Configuration
 	@ConditionalOnBean(name = "foo")
 	protected static class OnBeanNameConfiguration {
@@ -309,4 +319,35 @@ public class ConditionalOnBeanTests {
 
 	}
 
+	@Configuration
+	public static class OriginalDefinition {
+
+		@Bean
+		public String testBean() {
+			return "test";
+		}
+
+	}
+
+	@Configuration
+	@ConditionalOnBean(String.class)
+	public static class OverridingDefinition {
+
+		@Bean
+		public Integer testBean() {
+			return 1;
+		}
+
+	}
+
+	@Configuration
+	@ConditionalOnBean(String.class)
+	public static class ConsumingConfiguration {
+
+		ConsumingConfiguration(String testBean) {
+
+		}
+
+	}
+
 }