diff --git a/mlir/lib/IR/SymbolTable.cpp b/mlir/lib/IR/SymbolTable.cpp
--- a/mlir/lib/IR/SymbolTable.cpp
+++ b/mlir/lib/IR/SymbolTable.cpp
@@ -151,6 +151,7 @@
   }
 }
 
+// TODO: Consider if this should be renamed to something like insertOrUpdate
 /// Insert a new symbol into the table and associated operation, and rename it
 /// as necessary to avoid collisions.
 void SymbolTable::insert(Operation *symbol, Block::iterator insertPt) {
@@ -161,7 +162,11 @@
   assert(insertPt->getParentOp() == symbolTableOp &&
          "expected insertPt to be in the associated module operation");
 
-  body.getOperations().insert(insertPt, symbol);
+  // TODO: consider if SymbolTable's constructor should behave the same.
+  if (!symbol->getParentOp())
+    body.getOperations().insert(insertPt, symbol);
+  assert(symbol->getParentOp() == symbolTableOp &&
+         "smybol is already inserted in another op");
 
   // Add this symbol to the symbol table, uniquing the name if a conflict is
   // detected.