diff --git a/tmc-langs-r/src/main/java/fi/helsinki/cs/tmc/langs/r/RPlugin.java b/tmc-langs-r/src/main/java/fi/helsinki/cs/tmc/langs/r/RPlugin.java
index 579352cf5..620dcf040 100644
--- a/tmc-langs-r/src/main/java/fi/helsinki/cs/tmc/langs/r/RPlugin.java
+++ b/tmc-langs-r/src/main/java/fi/helsinki/cs/tmc/langs/r/RPlugin.java
@@ -121,6 +121,8 @@ public Optional<ExerciseDesc> scanExercise(Path path, String exerciseName) {
     @Override
     public RunResult runTests(Path path) {
         ProcessRunner runner = new ProcessRunner(getTestCommand(), path);
+
+        deleteResultsJson(path);
  
         try {
             ProcessResult result = runner.call();
@@ -189,6 +191,14 @@ public String[] getAvailablePointsCommand() {
         return ArrayUtils.addAll(command, args);
     }
 
+    public void deleteResultsJson(Path path) {
+        try {
+            Files.deleteIfExists(path.resolve(".results.json"));
+        } catch (Exception e) {
+            log.error("Could not delete .results.json", e);
+        }
+    }
+
     /**
      * No operation for now. To be possibly implemented later: remove .Rdata, .Rhistory etc
      */
diff --git a/tmc-langs-r/src/test/java/fi/helsinki/cs/tmc/langs/r/RPluginTest.java b/tmc-langs-r/src/test/java/fi/helsinki/cs/tmc/langs/r/RPluginTest.java
index 8646628e8..66b78cadd 100644
--- a/tmc-langs-r/src/test/java/fi/helsinki/cs/tmc/langs/r/RPluginTest.java
+++ b/tmc-langs-r/src/test/java/fi/helsinki/cs/tmc/langs/r/RPluginTest.java
@@ -120,7 +120,8 @@ public void runTestsReturnsStackTraceWhenPathDoesNotExist() {
         RunResult res = plugin.runTests(doesNotExist);
         
         String stackTrace = new String(res.logs.get(SpecialLogs.GENERIC_ERROR_MESSAGE));
-        assertEquals("java.lang.NullPointerException", stackTrace.split("\n")[0]);
+        assertEquals("java.lang.NullPointerException",
+                stackTrace.split(System.getProperty("line.separator"))[0]);
         assertTrue(stackTrace.split("\n").length > 1);
     }
     
@@ -155,4 +156,17 @@ public void getStudentFilePolicyReturnsRStudentFilePolicy() {
 
         assertTrue(policy instanceof RStudentFilePolicy);
     }
+
+    @Test
+    public void resultsJsonIsDeletedBeforeRunning() throws IOException {
+        Files.createFile(simpleAllTestsPassProject.resolve(".results.json"));
+        plugin.deleteResultsJson(simpleAllTestsPassProject);
+        assertTrue(!Files.exists(simpleAllTestsPassProject.resolve(".results.json")));
+    }
+
+    @Test
+    public void deleteResultsJsonWorksCorrectlyWhenNoJson() throws IOException {
+        plugin.deleteResultsJson(simpleAllTestsPassProject);
+        assertTrue(!Files.exists(simpleAllTestsPassProject.resolve(".results.json")));
+    }
 }