diff --git a/llvm/lib/Support/SmallVector.cpp b/llvm/lib/Support/SmallVector.cpp
--- a/llvm/lib/Support/SmallVector.cpp
+++ b/llvm/lib/Support/SmallVector.cpp
@@ -45,6 +45,12 @@
   if (MinCapacity > UINT32_MAX)
     report_bad_alloc_error("SmallVector capacity overflow during allocation");
 
+  // Ensure we can meet the guarantee of space for at least one more element.
+  // The above check alone will not catch the case where grow is called with a
+  // default MinCapacity of 0, but the current capacity cannot be increased.
+  if (capacity() == size_t(UINT32_MAX))
+    report_bad_alloc_error("SmallVector capacity unable to grow");
+
   size_t NewCapacity = 2 * capacity() + 1; // Always grow.
   NewCapacity =
       std::min(std::max(NewCapacity, MinCapacity), size_t(UINT32_MAX));