diff --git a/mlir/lib/Dialect/StandardOps/IR/Ops.cpp b/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
--- a/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
+++ b/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
@@ -622,8 +622,12 @@
     return emitOpError("incorrect number of results for callee");
 
   for (unsigned i = 0, e = fnType.getNumResults(); i != e; ++i)
-    if (getResult(i).getType() != fnType.getResult(i))
-      return emitOpError("result type mismatch");
+    if (getResult(i).getType() != fnType.getResult(i)) {
+      auto diag = emitOpError("result type mismatch at index ") << i;
+      diag.attachNote() << "      op result types: " << getResultTypes();
+      diag.attachNote() << "function result types: " << fnType.getResults();
+      return diag;
+    }
 
   return success();
 }