diff --git a/mlir/lib/Parser/Parser.cpp b/mlir/lib/Parser/Parser.cpp
--- a/mlir/lib/Parser/Parser.cpp
+++ b/mlir/lib/Parser/Parser.cpp
@@ -700,16 +700,35 @@
   // If we have already seen a value of this name, return it.
   if (useInfo.number < entries.size() && entries[useInfo.number].value) {
     Value result = entries[useInfo.number].value;
+
     // Check that the type matches the other uses.
-    if (result.getType() == type)
-      return maybeRecordUse(result);
-
-    emitError(useInfo.loc, "use of value '")
-        .append(useInfo.name,
-                "' expects different type than prior uses: ", type, " vs ",
-                result.getType())
-        .attachNote(getEncodedSourceLocation(entries[useInfo.number].loc))
-        .append("prior use here");
+    if (type && result.getType() != type) {
+      emitError(useInfo.loc, "use of value '")
+          .append(useInfo.name,
+                  "' expects different type than prior uses: ", type, " vs ",
+                  result.getType())
+          .attachNote(getEncodedSourceLocation(entries[useInfo.number].loc))
+          .append("prior use here");
+      return nullptr;
+    }
+
+    // Explicit type specification can be omitted, only if the Value was already
+    // defined prior in the same block.
+    if (!type && result.getParentBlock() != opBuilder.getBlock()) {
+      emitError(useInfo.loc, "value '")
+          .append(useInfo.name, "' was defined in separate block and requires "
+                                "explicit type definition")
+          .attachNote(getEncodedSourceLocation(entries[useInfo.number].loc))
+          .append("defined here");
+      return nullptr;
+    }
+
+    return maybeRecordUse(result);
+  }
+
+  if (!type) {
+    emitError(useInfo.loc, "forward reference of value '")
+        .append(useInfo.name, "' requires explicit type specification");
     return nullptr;
   }
 
diff --git a/mlir/test/IR/invalid.mlir b/mlir/test/IR/invalid.mlir
--- a/mlir/test/IR/invalid.mlir
+++ b/mlir/test/IR/invalid.mlir
@@ -1639,3 +1639,31 @@
 // -----
 
 func @foo() {} // expected-error {{expected non-empty function body}}
+
+// -----
+
+// expected-note@+1 {{defined here}}
+func @foo(%arg0: i64, %arg1: memref<1xf64>) {
+    br ^bb1
+
+  ^bb1:
+    // expected-error@+1 {{value '%arg1' was defined in separate block and requires explicit type definition}}
+    test.format_operand_optional_type_op %arg0, %arg1
+    return
+}
+
+// -----
+
+func @foo() {
+    br ^bb2
+
+  ^bb1:
+    // expected-error@+1 {{forward reference of value '%1' requires explicit type specification}}
+    test.format_operand_optional_type_op %0, %1
+    return
+
+  ^bb2:
+    %0 = arith.constant 0 : i64
+    %1 = memref.alloc() : memref<1xf64>
+    br ^bb1
+}
diff --git a/mlir/test/IR/parser.mlir b/mlir/test/IR/parser.mlir
--- a/mlir/test/IR/parser.mlir
+++ b/mlir/test/IR/parser.mlir
@@ -1470,3 +1470,13 @@
 // This is an unregister operation, the printing/parsing is handled by the dialect.
 // CHECK: test.dialect_custom_printer custom_format
 test.dialect_custom_printer custom_format
+
+// Can skip type definition for operands, if they are already defined in the same block
+// CHECK-LABEL: func @optional_operand_types
+func @optional_operand_types(%arg0: i64, %arg1: memref<1xf64>) {
+  // CHECK: test.format_operand_optional_type_op %arg0, %arg1
+  test.format_operand_optional_type_op %arg0, %arg1
+  // CHECK: test.format_operand_optional_type_op %arg0, %arg1
+  test.format_operand_optional_type_op %arg0, %arg1 : memref<1xf64>
+  return
+}
diff --git a/mlir/test/lib/Dialect/Test/TestDialect.cpp b/mlir/test/lib/Dialect/Test/TestDialect.cpp
--- a/mlir/test/lib/Dialect/Test/TestDialect.cpp
+++ b/mlir/test/lib/Dialect/Test/TestDialect.cpp
@@ -16,6 +16,7 @@
 #include "mlir/Dialect/Tensor/IR/Tensor.h"
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/DialectImplementation.h"
+#include "mlir/IR/OpImplementation.h"
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/IR/TypeUtilities.h"
 #include "mlir/Reducer/ReductionPatternInterface.h"
@@ -1095,6 +1096,34 @@
       /*printBlockTerminators=*/false);
 }
 
+//===----------------------------------------------------------------------===//
+// FormatOperandOptionalTypeOp
+//===----------------------------------------------------------------------===//
+
+static bool isDefinedAbove(Value val, Operation *op) {
+  if (val.isa<BlockArgument>())
+    return true;
+
+  return val.getDefiningOp()->getBlock() == op->getBlock() &&
+         val.getDefiningOp()->isBeforeInBlock(op);
+}
+
+static void printOptionalType(OpAsmPrinter &printer,
+                              FormatOperandOptionalTypeOp op, Type type) {
+  if (isDefinedAbove(op.operand(), op))
+    return;
+
+  printer << ":";
+  printer.printType(type);
+}
+
+static ParseResult parseOptionalType(OpAsmParser &parser, Type &type) {
+  if (parser.parseOptionalColon())
+    return success();
+
+  return parser.parseType(type);
+}
+
 #include "TestOpEnums.cpp.inc"
 #include "TestOpInterfaces.cpp.inc"
 #include "TestOpStructs.cpp.inc"
diff --git a/mlir/test/lib/Dialect/Test/TestOps.td b/mlir/test/lib/Dialect/Test/TestOps.td
--- a/mlir/test/lib/Dialect/Test/TestOps.td
+++ b/mlir/test/lib/Dialect/Test/TestOps.td
@@ -1757,6 +1757,9 @@
 def FormatOperandEOp : FormatOperandBase<"e", [{
   $buildable `,` $operand `:` type($buildable) `,` type($operand) attr-dict
 }]>;
+def FormatOperandOptionalTypeOp : FormatOperandBase<"optional_type", [{
+  $buildable `,` $operand custom<OptionalType>(type($operand)) attr-dict
+}]>;
 
 def FormatSuccessorAOp : TEST_Op<"format_successor_a_op", [Terminator]> {
   let successors = (successor VariadicSuccessor<AnySuccessor>:$targets);