diff --git a/pom.xml b/pom.xml
index a0018a0..a70298b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -126,7 +126,7 @@
       <dependency>
         <groupId>com.io7m.jaffirm</groupId>
         <artifactId>com.io7m.jaffirm.core</artifactId>
-        <version>4.0.0</version>
+        <version>4.0.1</version>
       </dependency>
 
       <!-- Build metadata. -->