diff --git a/lib/Analysis/BasicConstraintManager.cpp b/lib/Analysis/BasicConstraintManager.cpp
index a359b23..6f62c4b 100644
--- a/lib/Analysis/BasicConstraintManager.cpp
+++ b/lib/Analysis/BasicConstraintManager.cpp
@@ -369,8 +369,14 @@
   }
 
   const llvm::APSInt& Zero = getBasicVals().getZeroWithPtrWidth(false);
-  const llvm::APSInt& IdxV = cast<nonloc::ConcreteInt>(Idx).getValue();
-  const llvm::APSInt& UBV = cast<nonloc::ConcreteInt>(UpperBound).getValue();
+  llvm::APSInt IdxV = cast<nonloc::ConcreteInt>(Idx).getValue();
+  // IdxV might be too narrow.
+  if (IdxV.getBitWidth() < Zero.getBitWidth())
+    IdxV.extend(Zero.getBitWidth());
+  // UBV might be too narrow, too.
+  llvm::APSInt UBV = cast<nonloc::ConcreteInt>(UpperBound).getValue();
+  if (UBV.getBitWidth() < Zero.getBitWidth())
+    UBV.extend(Zero.getBitWidth());
 
   bool InBound = (Zero <= IdxV) && (IdxV < UBV);
 
diff --git a/lib/Analysis/RegionStore.cpp b/lib/Analysis/RegionStore.cpp
index 9a1f3ec..747b16d 100644
--- a/lib/Analysis/RegionStore.cpp
+++ b/lib/Analysis/RegionStore.cpp
@@ -254,12 +254,15 @@
   if ((CI1 = dyn_cast<nonloc::ConcreteInt>(&Idx)) &&
       (CI2 = dyn_cast<nonloc::ConcreteInt>(&Offset))) {
 
-    // Temporary SVal to hold a potential signed APSInt.
+    // Temporary SVal to hold a potential signed and extended APSInt.
     SVal SignedInt;
 
-    // Index might be unsigned. We have to convert it to signed.
-    if (CI2->getValue().isUnsigned()) {
+    // Index might be unsigned. We have to convert it to signed. It might also
+    // be less wide than the size. We have to extend it.
+    if (CI2->getValue().isUnsigned() ||
+        CI2->getValue().getBitWidth() < CI1->getValue().getBitWidth()) {
       llvm::APSInt SI = CI2->getValue();
+      SI.extend(CI1->getValue().getBitWidth());
       SI.setIsSigned(true);
       SignedInt = nonloc::ConcreteInt(getBasicVals().getValue(SI));
       CI2 = cast<nonloc::ConcreteInt>(&SignedInt);