diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/test/utils/TestingUtilities.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/test/utils/TestingUtilities.java
index 28fdf6d84..af854cd8a 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/test/utils/TestingUtilities.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/test/utils/TestingUtilities.java
@@ -151,13 +151,14 @@ public class TestingUtilities extends BaseTestingUtilities {
     String result = compareXml(f1, f2);
     if (result != null && SHOW_DIFF) {
       String diff = Utilities.path(System.getenv("ProgramFiles"), "WinMerge", "WinMergeU.exe");
-      List<String> command = new ArrayList<String>();
-      command.add("\"" + diff + "\" \"" + f1 + "\" \"" + f2 + "\"");
-
-      ProcessBuilder builder = new ProcessBuilder(command);
-      builder.directory(new CSFile("c:\\temp"));
-      builder.start();
+      if (new File(diff).exists()) {
+        List<String> command = new ArrayList<String>();
+        command.add("\"" + diff + "\" \"" + f1 + "\" \"" + f2 + "\"");
 
+        ProcessBuilder builder = new ProcessBuilder(command);
+        builder.directory(new CSFile("c:\\temp"));
+        builder.start();
+      }
     }
     return result;
   }