diff --git a/initializr-metadata/src/main/java/io/spring/initializr/metadata/BillOfMaterials.java b/initializr-metadata/src/main/java/io/spring/initializr/metadata/BillOfMaterials.java
index d5b8777e..7a3352ce 100644
--- a/initializr-metadata/src/main/java/io/spring/initializr/metadata/BillOfMaterials.java
+++ b/initializr-metadata/src/main/java/io/spring/initializr/metadata/BillOfMaterials.java
@@ -185,12 +185,13 @@ public class BillOfMaterials {
 	 * additional BOMs to use, if any.
 	 * @param bootVersion the Spring Boot version
 	 * @return the bill of materials
+	 * @throws InvalidInitializrMetadataException if no suitable mapping is found for that
+	 * version
 	 */
 	public BillOfMaterials resolve(Version bootVersion) {
 		if (this.mappings.isEmpty()) {
 			return this;
 		}
-
 		for (Mapping mapping : this.mappings) {
 			if (mapping.range.match(bootVersion)) {
 				BillOfMaterials resolvedBom = new BillOfMaterials(
@@ -205,7 +206,8 @@ public class BillOfMaterials {
 				return resolvedBom;
 			}
 		}
-		throw new IllegalStateException("No suitable mapping was found for " + this + " and version " + bootVersion);
+		throw new InvalidInitializrMetadataException(
+				"No suitable mapping was found for " + this + " and version " + bootVersion);
 	}
 
 	@Override
diff --git a/initializr-metadata/src/test/java/io/spring/initializr/metadata/BillOfMaterialsTests.java b/initializr-metadata/src/test/java/io/spring/initializr/metadata/BillOfMaterialsTests.java
index 659eb9ea..bc4c6ee3 100755
--- a/initializr-metadata/src/test/java/io/spring/initializr/metadata/BillOfMaterialsTests.java
+++ b/initializr-metadata/src/test/java/io/spring/initializr/metadata/BillOfMaterialsTests.java
@@ -24,7 +24,7 @@ import io.spring.initializr.metadata.BillOfMaterials.Mapping;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 
 /**
  * @author Stephane Nicoll
@@ -119,8 +119,8 @@ class BillOfMaterialsTests {
 		bom.getMappings().add(Mapping.create("[1.2.0.RELEASE,1.3.0.M1)", "1.1.0"));
 		bom.getMappings().add(Mapping.create("[1.3.0.M1, 1.4.0.M1)", "1.2.0"));
 		bom.validate();
-		assertThatIllegalStateException().isThrownBy(() -> bom.resolve(Version.parse("1.4.1.RELEASE")))
-				.withMessageContaining("1.4.1.RELEASE");
+		assertThatExceptionOfType(InvalidInitializrMetadataException.class)
+				.isThrownBy(() -> bom.resolve(Version.parse("1.4.1.RELEASE"))).withMessageContaining("1.4.1.RELEASE");
 	}
 
 	@Test
diff --git a/initializr-web/src/main/java/io/spring/initializr/web/controller/ProjectMetadataController.java b/initializr-web/src/main/java/io/spring/initializr/web/controller/ProjectMetadataController.java
index 98a58db7..4b69b526 100644
--- a/initializr-web/src/main/java/io/spring/initializr/web/controller/ProjectMetadataController.java
+++ b/initializr-web/src/main/java/io/spring/initializr/web/controller/ProjectMetadataController.java
@@ -16,13 +16,17 @@
 
 package io.spring.initializr.web.controller;
 
+import java.io.IOException;
 import java.util.concurrent.TimeUnit;
 
+import javax.servlet.http.HttpServletResponse;
+
 import io.spring.initializr.generator.version.Version;
 import io.spring.initializr.metadata.DependencyMetadata;
 import io.spring.initializr.metadata.DependencyMetadataProvider;
 import io.spring.initializr.metadata.InitializrMetadata;
 import io.spring.initializr.metadata.InitializrMetadataProvider;
+import io.spring.initializr.metadata.InvalidInitializrMetadataException;
 import io.spring.initializr.web.mapper.DependencyMetadataV21JsonMapper;
 import io.spring.initializr.web.mapper.InitializrMetadataJsonMapper;
 import io.spring.initializr.web.mapper.InitializrMetadataV21JsonMapper;
@@ -30,9 +34,11 @@ import io.spring.initializr.web.mapper.InitializrMetadataV2JsonMapper;
 import io.spring.initializr.web.mapper.InitializrMetadataVersion;
 
 import org.springframework.http.CacheControl;
+import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.ResponseBody;
@@ -85,6 +91,12 @@ public class ProjectMetadataController extends AbstractMetadataController {
 		return dependenciesFor(InitializrMetadataVersion.V2_1, bootVersion);
 	}
 
+	@ExceptionHandler
+	public void invalidMetadataRequest(HttpServletResponse response, InvalidInitializrMetadataException ex)
+			throws IOException {
+		response.sendError(HttpStatus.BAD_REQUEST.value(), ex.getMessage());
+	}
+
 	/**
 	 * Return the {@link CacheControl} response headers to use for the specified
 	 * {@link InitializrMetadata metadata}. If no cache should be applied
diff --git a/initializr-web/src/test/java/io/spring/initializr/web/controller/ProjectMetadataControllerIntegrationTests.java b/initializr-web/src/test/java/io/spring/initializr/web/controller/ProjectMetadataControllerIntegrationTests.java
index 2b6d5ea2..55472cba 100644
--- a/initializr-web/src/test/java/io/spring/initializr/web/controller/ProjectMetadataControllerIntegrationTests.java
+++ b/initializr-web/src/test/java/io/spring/initializr/web/controller/ProjectMetadataControllerIntegrationTests.java
@@ -60,6 +60,18 @@ public class ProjectMetadataControllerIntegrationTests extends AbstractInitializ
 		validateMetadata(response, InitializrMetadataVersion.V2.getMediaType(), "2.0.0", JSONCompareMode.STRICT);
 	}
 
+	@Test
+	void metadataWithInvalidPlatformVersion() {
+		try {
+			execute("/dependencies?bootVersion=1.5.17.RELEASE", String.class, "application/vnd.initializr.v2.1+json",
+					"application/json");
+		}
+		catch (HttpClientErrorException ex) {
+			assertThat(ex.getStatusCode()).isEqualTo(HttpStatus.BAD_REQUEST);
+			assertThat(ex.getResponseBodyAsString().contains("1.5.17.RELEASE"));
+		}
+	}
+
 	@Test
 	void metadataWithCurrentAcceptHeader() {
 		getRequests().setFields("_links.maven-project", "dependencies.values[0]", "type.values[0]",