Index: include/llvm/FuzzMutate/OpDescriptor.h
===================================================================
--- include/llvm/FuzzMutate/OpDescriptor.h
+++ include/llvm/FuzzMutate/OpDescriptor.h
@@ -164,6 +164,14 @@
 
 static inline SourcePred anyAggregateType() {
   auto Pred = [](ArrayRef<Value *>, const Value *V) {
+    // We can't index zero sized arrays.
+    if (isa<ArrayType>(V->getType()))
+      return V->getType()->getArrayNumElements() > 0;
+
+    // Structs can also be zero sized. I.e opaque types.
+    if (isa<StructType>(V->getType()))
+      return V->getType()->getStructNumElements() > 0;
+
     return V->getType()->isAggregateType();
   };
   // TODO: For now we only find aggregates in BaseTypes. It might be better to
Index: unittests/FuzzMutate/OperationsTest.cpp
===================================================================
--- unittests/FuzzMutate/OperationsTest.cpp
+++ unittests/FuzzMutate/OperationsTest.cpp
@@ -307,6 +307,7 @@
 
   Type *StructTy = StructType::create(Ctx, {Int8PtrTy, Int32Ty});
   Type *OpaqueTy = StructType::create(Ctx, "OpaqueStruct");
+  Type *ZeroSizedArrayTy = ArrayType::get(Int64Ty, 0);
   Type *ArrayTy = ArrayType::get(Int64Ty, 4);
   Type *VectorTy = VectorType::get(Int32Ty, 2);
 
@@ -317,17 +318,22 @@
   Constant *SVal = UndefValue::get(StructTy);
   Constant *OVal = UndefValue::get(OpaqueTy);
   Constant *AVal = UndefValue::get(ArrayTy);
+  Constant *ZAVal = UndefValue::get(ZeroSizedArrayTy);
   Constant *VVal = UndefValue::get(VectorTy);
 
   EXPECT_TRUE(EVOp.SourcePreds[0].matches({}, SVal));
-  EXPECT_TRUE(EVOp.SourcePreds[0].matches({}, OVal));
+  EXPECT_FALSE(EVOp.SourcePreds[0].matches({}, OVal));
   EXPECT_TRUE(EVOp.SourcePreds[0].matches({}, AVal));
   EXPECT_FALSE(EVOp.SourcePreds[0].matches({}, VVal));
   EXPECT_TRUE(IVOp.SourcePreds[0].matches({}, SVal));
-  EXPECT_TRUE(IVOp.SourcePreds[0].matches({}, OVal));
+  EXPECT_FALSE(IVOp.SourcePreds[0].matches({}, OVal));
   EXPECT_TRUE(IVOp.SourcePreds[0].matches({}, AVal));
   EXPECT_FALSE(IVOp.SourcePreds[0].matches({}, VVal));
 
+  // Don't consider zero sized arrays as viable sources
+  EXPECT_FALSE(EVOp.SourcePreds[0].matches({}, ZAVal));
+  EXPECT_FALSE(IVOp.SourcePreds[0].matches({}, ZAVal));
+
   // Make sure we're range checking appropriately.
   EXPECT_TRUE(
       EVOp.SourcePreds[1].matches({SVal}, ConstantInt::get(Int32Ty, 0)));