diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index a42a366..9bad0d3 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -547,6 +547,7 @@
       minReg = reg;
     }
   }
+  assert(minReg && "Didn't find any reg!");
   DEBUG(std::cerr << "\t\tregister with min weight: "
         << mri_->getName(minReg) << " (" << minWeight << ")\n");