diff --git a/src/main/java/com/greghaskins/spectrum/Spectrum.java b/src/main/java/com/greghaskins/spectrum/Spectrum.java
index 45a9542..d79dfcf 100644
--- a/src/main/java/com/greghaskins/spectrum/Spectrum.java
+++ b/src/main/java/com/greghaskins/spectrum/Spectrum.java
@@ -146,7 +146,7 @@ public void run(final RunNotifier notifier) {
         this.rootSuite.run(notifier);
     }
 
-    private static void beginDefintion(final Suite suite, final Block definitionBlock) {
+    synchronized private static void beginDefintion(final Suite suite, final Block definitionBlock) {
         suiteStack.push(suite);
         try {
             definitionBlock.run();
@@ -156,7 +156,7 @@ private static void beginDefintion(final Suite suite, final Block definitionBloc
         suiteStack.pop();
     }
 
-    private static Suite getCurrentSuite() {
+    synchronized private static Suite getCurrentSuite() {
         return suiteStack.peek();
     }