diff --git a/honoka/plugins/primeprediction.cpp b/honoka/plugins/primeprediction.cpp
index 256a0da..b56e04d 100644
--- a/honoka/plugins/primeprediction.cpp
+++ b/honoka/plugins/primeprediction.cpp
@@ -37,6 +37,7 @@
 #endif
 
 #include <sys/types.h>
+#include <signal.h>
 #include <sys/wait.h>
 #include <sys/shm.h>