diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index d43cc19..144f0a7 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -685,8 +685,14 @@
     }
 
     // All registers must have inf weight. Just grab one!
-    if (!minReg)
+    if (!minReg) {
+      if (active_.size() == 0) {
+        // FIXME: All the registers are occupied by fixed intervals.
+        cerr << "Register allocator ran out of registers!\n";
+        abort();
+      }
       minReg = *RC->allocation_order_begin(*mf_);
+    }
   }
   
   DOUT << "\t\tregister with min weight: "