Index: include/clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h
===================================================================
--- include/clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h
+++ include/clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h
@@ -211,7 +211,8 @@
   }
 
   const llvm::APSInt &getTruthValue(bool b, QualType T) {
-    return getValue(b ? 1 : 0, Ctx.getIntWidth(T), true);
+    return getValue(b ? 1 : 0, Ctx.getIntWidth(T),
+                    T->isUnsignedIntegerOrEnumerationType());
   }
 
   const llvm::APSInt &getTruthValue(bool b) {
Index: test/Analysis/casts.c
===================================================================
--- test/Analysis/casts.c
+++ test/Analysis/casts.c
@@ -182,3 +182,9 @@
     c += 1;
   }
 }
+
+void testSwitchWithSizeofs() {
+  switch (sizeof(char) == 1) { // expected-warning{{switch condition has boolean value}}
+  case sizeof(char):; // no-crash
+  }
+}