diff --git a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
--- a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
+++ b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
@@ -1556,6 +1556,12 @@
 }
 
 static void print(OpAsmPrinter &p, AffineForOp op) {
+  if (op.getRegion().empty()) {
+    p << " <<EMPTY REGION - INVALID>> ";
+    p.printGenericOp(op, false);
+    return;
+  }
+
   p << ' ';
   p.printOperand(op.getBody()->getArgument(0));
   p << " = ";
@@ -3136,6 +3142,12 @@
 }
 
 static void print(OpAsmPrinter &p, AffineParallelOp op) {
+  if (op.getRegion().empty()) {
+    p << " <<EMPTY REGION - INVALID>> ";
+    p.printGenericOp(op, false);
+    return;
+  }
+
   p << " (" << op.getBody()->getArguments() << ") = (";
   printMinMaxBound(p, op.lowerBoundsMapAttr(), op.lowerBoundsGroupsAttr(),
                    op.getLowerBoundsOperands(), "max");
diff --git a/mlir/lib/Dialect/SCF/SCF.cpp b/mlir/lib/Dialect/SCF/SCF.cpp
--- a/mlir/lib/Dialect/SCF/SCF.cpp
+++ b/mlir/lib/Dialect/SCF/SCF.cpp
@@ -341,6 +341,12 @@
 }
 
 static void print(OpAsmPrinter &p, ForOp op) {
+  if (op.getRegion().empty()) {
+    p << " <<EMPTY REGION - INVALID>> ";
+    p.printGenericOp(op, false);
+    return;
+  }
+
   p << " " << op.getInductionVar() << " = " << op.getLowerBound() << " to "
     << op.getUpperBound() << " step " << op.getStep();
 
@@ -1843,6 +1849,12 @@
 }
 
 static void print(OpAsmPrinter &p, ParallelOp op) {
+  if (op.getRegion().empty()) {
+    p << " <<EMPTY REGION - INVALID>> ";
+    p.printGenericOp(op, false);
+    return;
+  }
+
   p << " (" << op.getBody()->getArguments() << ") = (" << op.getLowerBound()
     << ") to (" << op.getUpperBound() << ") step (" << op.getStep() << ")";
   if (!op.getInitVals().empty())
@@ -2217,6 +2229,12 @@
 
 /// Prints a `while` op.
 static void print(OpAsmPrinter &p, scf::WhileOp op) {
+  if (op.getBefore().empty() || op.getAfter().empty()) {
+    p << " <<EMPTY REGION - INVALID>> ";
+    p.printGenericOp(op, false);
+    return;
+  }
+
   printInitializationList(p, op.getBefore().front().getArguments(),
                           op.getInits(), " ");
   p << " : ";
diff --git a/mlir/test/Conversion/AffineToStandard/lower-affine.mlir b/mlir/test/Conversion/AffineToStandard/lower-affine.mlir
--- a/mlir/test/Conversion/AffineToStandard/lower-affine.mlir
+++ b/mlir/test/Conversion/AffineToStandard/lower-affine.mlir
@@ -1,4 +1,5 @@
-// RUN: mlir-opt -lower-affine %s | FileCheck %s
+// `-debug` is used here to check that we don't crash when it's specified.
+// RUN: mlir-opt -lower-affine -debug %s | FileCheck %s
 
 // CHECK-LABEL: func @empty() {
 func @empty() {
diff --git a/mlir/test/Conversion/SCFToStandard/convert-to-cfg.mlir b/mlir/test/Conversion/SCFToStandard/convert-to-cfg.mlir
--- a/mlir/test/Conversion/SCFToStandard/convert-to-cfg.mlir
+++ b/mlir/test/Conversion/SCFToStandard/convert-to-cfg.mlir
@@ -1,4 +1,5 @@
-// RUN: mlir-opt -allow-unregistered-dialect -convert-scf-to-std %s | FileCheck %s
+// `-debug` is used here to check that we don't crash when it's specified.
+// RUN: mlir-opt -allow-unregistered-dialect -convert-scf-to-std -debug %s | FileCheck %s
 
 // CHECK-LABEL: func @simple_std_for_loop(%{{.*}}: index, %{{.*}}: index, %{{.*}}: index) {
 //  CHECK-NEXT:  br ^bb1(%{{.*}} : index)