diff --git a/clang/test/Analysis/z3-crosscheck.c b/clang/test/Analysis/z3-crosscheck.c
--- a/clang/test/Analysis/z3-crosscheck.c
+++ b/clang/test/Analysis/z3-crosscheck.c
@@ -77,3 +77,15 @@
     // expected-warning@-1{{garbage}}
   }
 }
+
+// don't crash, and also produce a core.CallAndMessage finding
+void a(int);
+typedef struct {
+  int b;
+} c;
+c *d;
+void e() {
+  (void)d->b;
+  int f;
+  a(f); // expected-warning {{1st function call argument is an uninitialized value [core.CallAndMessage]}}
+}
diff --git a/llvm/lib/Support/Z3Solver.cpp b/llvm/lib/Support/Z3Solver.cpp
--- a/llvm/lib/Support/Z3Solver.cpp
+++ b/llvm/lib/Support/Z3Solver.cpp
@@ -729,7 +729,7 @@
     const Z3_sort Z3Sort = toZ3Sort(*getBitvectorSort(BitWidth)).Sort;
 
     // Slow path, when 64 bits are not enough.
-    if (LLVM_UNLIKELY(Int.getBitWidth() > 64u)) {
+    if (LLVM_UNLIKELY(!Int.isRepresentableByInt64())) {
       SmallString<40> Buffer;
       Int.toString(Buffer, 10);
       return newExprRef(Z3Expr(