diff --git a/honoka/plugins/primeprediction.cpp b/honoka/plugins/primeprediction.cpp
index a4e6ed5..a4cd5f6 100644
--- a/honoka/plugins/primeprediction.cpp
+++ b/honoka/plugins/primeprediction.cpp
@@ -209,6 +209,18 @@
 bool PrimePrediction::connect()
 {
     if (mid == -1) return false;
+    
+    // primeチェーック！
+    int ps;
+    if (fork() == 0) {
+        execlp("prime","--help",NULL);
+        _exit(0);
+    }
+    wait(&ps);
+    if (!WIFEXITED(ps)) return false;
+    if (WEXITSTATUS(ps) != 0) return false;
+    // primeは動いてるっぽい。以下。
+    
     int in_fd[2],out_fd[2],i;
     if (con[0]) return true;
     if (pipe(in_fd) == -1) return false;