diff --git a/cell.cpp b/cell.cpp
index 6e4c3dd6..6533c23b 100644
--- a/cell.cpp
+++ b/cell.cpp
@@ -908,7 +908,7 @@ vector<cell*> build_shortest_path(cell *c1, cell *c2) {
     while(c1 != c2) {
       p.push_back(c1);
       forCellCM(c, c1) if(celldist(c) < celldist(c1)) { c1 = c; goto next1; }
-      println(hlog, "could not build_shortest_path"); exit(1);
+      throw hr_shortest_path_exception();
       next1: ;
       }
     p.push_back(c1);
@@ -921,7 +921,7 @@ vector<cell*> build_shortest_path(cell *c1, cell *c2) {
     while(c1 != c2) {
       p.push_back(c1);
       forCellCM(c, c1) if(celldistance(c, c2) < celldistance(c1, c2)) { c1 = c; goto next; }
-      println(hlog, "could not build_shortest_path"); exit(1);
+      throw hr_shortest_path_exception();
       next: ;
       }
     p.push_back(c1);
diff --git a/hyper.h b/hyper.h
index 602194e9..af8e6e83 100644
--- a/hyper.h
+++ b/hyper.h
@@ -79,6 +79,9 @@ using std::asinh;
 using std::acosh;
 #endif
 
+struct hr_exception: std::exception { hr_exception() {} };
+struct hr_shortest_path_exception: hr_exception { };
+
 // genus (in grammar)
 #define GEN_M 0
 #define GEN_F 1
@@ -4547,7 +4550,7 @@ template<class T, class U> void hread(hstream& hs, map<T,U>& a) {
 template<class C, class C1, class... CS> void hwrite(hstream& hs, const C& c, const C1& c1, const CS&... cs) { hwrite(hs, c); hwrite(hs, c1, cs...); }
 template<class C, class C1, class... CS> void hread(hstream& hs, C& c, C1& c1, CS&... cs) { hread(hs, c); hread(hs, c1, cs...); }
 
-struct hstream_exception : std::exception { hstream_exception() {} };
+struct hstream_exception : hr_exception { hstream_exception() {} };
 
 struct fhstream : hstream {
   FILE *f;
diff --git a/racing.cpp b/racing.cpp
index d40027d6..f3d8e26d 100644
--- a/racing.cpp
+++ b/racing.cpp
@@ -301,8 +301,15 @@ void generate_track() {
       }
     }
 
-  track = build_shortest_path(s, goal);
-  
+  try {
+    track = build_shortest_path(s, goal);
+    }
+  catch(hr_shortest_path_exception&) {
+    addMessage("error: could not build path");
+    gamegen_failure = true;
+    racing::on = false;
+    return;
+    }  
   
   /*
   transmatrix At = spin(hrand(1000));