diff --git a/objectivec/GPBCodedInputStream.m b/objectivec/GPBCodedInputStream.m
index eaa28e5..319ec15 100644
--- a/objectivec/GPBCodedInputStream.m
+++ b/objectivec/GPBCodedInputStream.m
@@ -219,15 +219,16 @@
     result = [[NSString alloc] initWithBytes:&state->bytes[state->bufferPos]
                                       length:size
                                     encoding:NSUTF8StringEncoding];
+    state->bufferPos += size;
     if (!result) {
-      result = @"";
 #ifdef DEBUG
       // https://developers.google.com/protocol-buffers/docs/proto#scalar
-      NSLog(@"UTF8 failure, is some field type 'string' when it should be "
+      NSLog(@"UTF-8 failure, is some field type 'string' when it should be "
             @"'bytes'?");
 #endif
+      [NSException raise:NSParseErrorException
+                  format:@"Invalid UTF-8 for a 'string'"];
     }
-    state->bufferPos += size;
   }
   return result;
 }
diff --git a/objectivec/Tests/GPBCodedInputStreamTests.m b/objectivec/Tests/GPBCodedInputStreamTests.m
index b40360e..cc40215 100644
--- a/objectivec/Tests/GPBCodedInputStreamTests.m
+++ b/objectivec/Tests/GPBCodedInputStreamTests.m
@@ -283,16 +283,15 @@
   [output writeRawData:[NSData dataWithBytes:bytes length:sizeof(bytes)]];
   [output flush];
 
-  NSData* data =
+  NSData *data =
       [rawOutput propertyForKey:NSStreamDataWrittenToMemoryStreamKey];
   GPBCodedInputStream* input = [GPBCodedInputStream streamWithData:data];
+  NSError *error = nil;
   TestAllTypes* message = [TestAllTypes parseFromCodedInputStream:input
                                                 extensionRegistry:nil
-                                                            error:NULL];
-  XCTAssertNotNil(message);
-  // Make sure we can read string properties twice without crashing.
-  XCTAssertEqual([message.defaultString length], (NSUInteger)0);
-  XCTAssertEqualObjects(@"", message.defaultString);
+                                                            error:&error];
+  XCTAssertNotNil(error);
+  XCTAssertNil(message);
 }
 
 - (void)testBOMWithinStrings {