diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index c615df1..439e3b6 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -1897,7 +1897,8 @@
 static bool NoEscapeForStringBufferReference(HInstruction* reference, HInstruction* user) {
   if (user->IsInvokeStaticOrDirect()) {
     // Any constructor on StringBuffer is okay.
-    return user->AsInvokeStaticOrDirect()->GetResolvedMethod()->IsConstructor() &&
+    return user->AsInvokeStaticOrDirect()->GetResolvedMethod() != nullptr &&
+           user->AsInvokeStaticOrDirect()->GetResolvedMethod()->IsConstructor() &&
            user->InputAt(0) == reference;
   } else if (user->IsInvokeVirtual()) {
     switch (user->AsInvokeVirtual()->GetIntrinsic()) {
diff --git a/test/624-checker-stringops/src/Main.java b/test/624-checker-stringops/src/Main.java
index d965e3f..75b782e 100644
--- a/test/624-checker-stringops/src/Main.java
+++ b/test/624-checker-stringops/src/Main.java
@@ -258,6 +258,20 @@
     return b.length();
   }
 
+  // Regression b/33656359: StringBuffer x is passed to constructor of String
+  // (this caused old code to crash due to missing nullptr check).
+  //
+  /// CHECK-START: void Main.doesNothing() instruction_simplifier (before)
+  /// CHECK-DAG: InvokeVirtual intrinsic:StringBufferToString
+  //
+  /// CHECK-START: void Main.doesNothing() instruction_simplifier (after)
+  /// CHECK-DAG: InvokeVirtual intrinsic:StringBufferToString
+  static void doesNothing() {
+    StringBuffer x = new StringBuffer();
+    String y = new String(x);
+    x.toString();
+  }
+
   public static void main(String[] args) {
     expectEquals(1865, liveIndexOf());
     expectEquals(29, deadIndexOf());
@@ -281,6 +295,8 @@
     expectEquals(0, bufferDeadLoop());
     expectEquals(0, builderDeadLoop());
 
+    doesNothing();
+
     System.out.println("passed");
   }