diff --git a/mlir/lib/Dialect/Traits.cpp b/mlir/lib/Dialect/Traits.cpp
--- a/mlir/lib/Dialect/Traits.cpp
+++ b/mlir/lib/Dialect/Traits.cpp
@@ -202,10 +202,16 @@
     // inferredDim  existingDim  Behavior
     // -----------  -----------  --------
     // dynamic      dynamic      OK
-    // dynamic      static       Error
+    // dynamic      static       OK^1
     // static       dynamic      OK
     // static       static       OK if equal
-    return ShapedType::isDynamic(existingDim) || inferredDim == existingDim;
+    //
+    // [1] This allows for implicit dynamic-to-static cast with undefined
+    // behavior if the resulting runtime dimension size does not match the given
+    // static size. This is meant to only flag known invalid cases while the
+    // expectation is that these should be equal dynamically.
+    return ShapedType::isDynamic(existingDim) ||
+           ShapedType::isDynamic(inferredDim) || inferredDim == existingDim;
   };
   if (inferred.size() != existing.size())
     return false;
diff --git a/mlir/test/Dialect/traits.mlir b/mlir/test/Dialect/traits.mlir
--- a/mlir/test/Dialect/traits.mlir
+++ b/mlir/test/Dialect/traits.mlir
@@ -111,9 +111,10 @@
 
 // -----
 
-// Error for inferred dynamic dimension but existing static dimensions
+// Error for inferred dynamic dimension but existing static dimensions, this
+// has moved to runtime UB if not matching.
 func.func @broadcast_tensor_tensor_tensor(%arg0: tensor<?xi32>, %arg1: tensor<?xi32>) -> tensor<2xi32> {
-  // expected-error @+1 {{op result type '2' not broadcast compatible with broadcasted operands's shapes '?'}}
+  // not-error @+1 {{op result type '2' not broadcast compatible with broadcasted operands's shapes '?'}}
   %0 = "test.broadcastable"(%arg0, %arg1) : (tensor<?xi32>, tensor<?xi32>) -> tensor<2xi32>
   return %0 : tensor<2xi32>
 }