diff --git a/spring-graphql/src/main/java/org/springframework/graphql/client/ResponseMapGraphQlResponse.java b/spring-graphql/src/main/java/org/springframework/graphql/client/ResponseMapGraphQlResponse.java
index d8f08951..22f82976 100644
--- a/spring-graphql/src/main/java/org/springframework/graphql/client/ResponseMapGraphQlResponse.java
+++ b/spring-graphql/src/main/java/org/springframework/graphql/client/ResponseMapGraphQlResponse.java
@@ -16,11 +16,9 @@
 
 package org.springframework.graphql.client;
 
-import java.math.BigInteger;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.Objects;
 import java.util.stream.Collectors;
 
 import graphql.ErrorClassification;
@@ -125,29 +123,28 @@ class ResponseMapGraphQlResponse extends AbstractGraphQlResponse {
 		MapResponseError(Map<String, Object> errorMap) {
 			Assert.notNull(errorMap, "'errorMap' is required");
 			this.errorMap = errorMap;
-			this.locations = initLocations(errorMap);
+			this.locations = initSourceLocations(errorMap);
 			this.path = initPath(errorMap);
 		}
 
 		@SuppressWarnings("unchecked")
-		private static List<SourceLocation> initLocations(Map<String, Object> errorMap) {
-			return ((List<Map<String, Object>>) errorMap.getOrDefault("locations", Collections.emptyList())).stream()
-					.map(map -> new SourceLocation(
-						objectAsInt(map.get("line")),
-						objectAsInt(map.get("column")),
-						Objects.toString(map.get("sourceName"))
-					))
+		private static List<SourceLocation> initSourceLocations(Map<String, Object> errorMap) {
+			List<Map<String, Object>> locations = (List<Map<String, Object>>) errorMap.get("locations");
+			if (locations == null) {
+				return Collections.emptyList();
+			}
+			return locations.stream()
+					.map(m -> new SourceLocation(getInt(m, "line"), getInt(m, "column"), (String) m.get("sourceName")))
 					.collect(Collectors.toList());
 		}
 
-		private static int objectAsInt(Object value) {
-
-			if (value instanceof BigInteger bigInteger) {
-				return bigInteger.intValue();
-			} else if (value instanceof Number number) {
+		private static int getInt(Map<String, Object> map, String key) {
+			if (map.get(key) instanceof Number number) {
 				return number.intValue();
-			} else {
-				return -1;
+			}
+			else {
+				throw new IllegalArgumentException(
+						"Expected integer value: " + ObjectUtils.nullSafeClassName(map.get(key)));
 			}
 		}
 
@@ -162,6 +159,7 @@ class ResponseMapGraphQlResponse extends AbstractGraphQlResponse {
 					(s, s2) -> null);
 		}
 
+
 		@Override
 		@Nullable
 		public String getMessage() {
diff --git a/spring-graphql/src/test/java/org/springframework/graphql/client/DefaultGraphQlClientResponseTests.java b/spring-graphql/src/test/java/org/springframework/graphql/client/DefaultGraphQlClientResponseTests.java
index 666198ca..c39be5a3 100644
--- a/spring-graphql/src/test/java/org/springframework/graphql/client/DefaultGraphQlClientResponseTests.java
+++ b/spring-graphql/src/test/java/org/springframework/graphql/client/DefaultGraphQlClientResponseTests.java
@@ -138,24 +138,19 @@ public class DefaultGraphQlClientResponseTests {
 		assertThat(errors.get(2).getPath()).isEqualTo("me.friends[0].name");
 	}
 
-	@Test
+	@Test // gh-849
 	void errorWithBigIntegerNumbers() throws IOException {
 
 		String path = "me.friends";
+		GraphQLError error = createError("/me", "fail-me", new SourceLocation(100, 100));
 
-		GraphQLError error0 = createError("/me", "fail-me", new SourceLocation(100, 100));
+		ObjectMapper mapper = new ObjectMapper().enable(DeserializationFeature.USE_BIG_INTEGER_FOR_INTS);
+		Map<?, ?> errorMap = mapper.readValue(mapper.writeValueAsString(error), Map.class);
 
-		ObjectMapper objectMapper = new ObjectMapper().enable(DeserializationFeature.USE_BIG_INTEGER_FOR_INTS);
-		String error0string = objectMapper.writeValueAsString(error0);
-		Map<?, ?> error0Map = objectMapper.readValue(error0string, Map.class);
-
-		List<?> list = List.of(error0Map);
-
-		ClientGraphQlResponse response = createResponse(Collections.singletonMap("errors", list));
+		ClientGraphQlResponse response = createResponse(Collections.singletonMap("errors", List.of(errorMap)));
 		ClientResponseField field =  response.field(path);
 
 		List<ResponseError> errors = field.getErrors();
-
 		assertThat(errors).hasSize(1);
 		assertThat(errors.get(0).getPath()).isEqualTo("me");
 		assertThat(errors.get(0).getLocations().get(0).getLine()).isEqualTo(100);