--- a/test/langtools/tools/javac/lib/combo/ComboInstance.java	Mon Oct 21 15:11:44 2019 +0200
+++ b/test/langtools/tools/javac/lib/combo/ComboInstance.java	Mon Oct 21 15:38:26 2019 +0200
@@ -23,6 +23,7 @@
 
 package combo;
 
+import java.lang.reflect.Method;
 import javax.tools.StandardJavaFileManager;
 import java.util.Optional;
 
@@ -57,6 +58,14 @@
             env.info().lastError = Optional.of(ex);
         } finally {
             this.env = null;
+            try {
+                Class<?> fmClass = env.fileManager().getClass();
+                Method clear = fmClass.getMethod("clear");
+                clear.setAccessible(true);
+                clear.invoke(env.fileManager());
+            } catch (Exception ex) {
+                throw new IllegalStateException(ex);
+            }
         }
     }
 
@@ -125,4 +134,4 @@
             return success;
         }
     }
-}
\ No newline at end of file
+}