diff --git a/flang/runtime/format-implementation.h b/flang/runtime/format-implementation.h
--- a/flang/runtime/format-implementation.h
+++ b/flang/runtime/format-implementation.h
@@ -225,6 +225,7 @@
   while (true) {
     std::optional<int> repeat;
     bool unlimited{false};
+    auto maybeReversionPoint{offset_};
     CharType ch{GetNextChar(context)};
     while (ch == ',' || ch == ':') {
       // Skip commas, and don't complain if they're missing; the format
@@ -254,6 +255,7 @@
         return 0;
       }
       stack_[height_].start = offset_ - 1; // the '('
+      RUNTIME_CHECK(context, format_[stack_[height_].start] == '(');
       if (unlimited || height_ == 0) {
         stack_[height_].remaining = Iteration::unlimited;
         unlimitedLoopCheck = offset_ - 1;
@@ -265,6 +267,12 @@
       } else {
         stack_[height_].remaining = 0;
       }
+      if (height_ == 1) {
+        // Subtle point (F'2018 13.4 para 9): tha last parenthesized group
+        // at height 1 becomes the restart point after control reaches the
+        // end of the format, including its repeat count.
+        stack_[0].start = maybeReversionPoint - 1;
+      }
       ++height_;
     } else if (height_ == 0) {
       context.SignalError(IostatErrorInFormat, "FORMAT lacks initial '('");
@@ -276,14 +284,15 @@
         }
         context.AdvanceRecord(); // implied / before rightmost )
       }
+      auto restart{stack_[height_ - 1].start + 1};
       if (stack_[height_ - 1].remaining == Iteration::unlimited) {
-        offset_ = stack_[height_ - 1].start + 1;
+        offset_ = restart;
         if (offset_ == unlimitedLoopCheck) {
           context.SignalError(IostatErrorInFormat,
               "Unlimited repetition in FORMAT lacks data edit descriptors");
         }
       } else if (stack_[height_ - 1].remaining-- > 0) {
-        offset_ = stack_[height_ - 1].start + 1;
+        offset_ = restart;
       } else {
         --height_;
       }
@@ -396,7 +405,7 @@
     ++height_;
   }
   edit.repeat = 1;
-  if (height_ > 1) {
+  if (height_ > 1) { // Subtle: stack_[0].start doesn't necessarily point to '('
     int start{stack_[height_ - 1].start};
     if (format_[start] != '(') {
       if (stack_[height_ - 1].remaining > maxRepeat) {
diff --git a/flang/unittests/Runtime/hello.cpp b/flang/unittests/Runtime/hello.cpp
--- a/flang/unittests/Runtime/hello.cpp
+++ b/flang/unittests/Runtime/hello.cpp
@@ -38,16 +38,16 @@
 }
 
 static void multiline() {
-  char buffer[4][32];
+  char buffer[5][32];
   StaticDescriptor<1> staticDescriptor[2];
   Descriptor &whole{staticDescriptor[0].descriptor()};
-  SubscriptValue extent[]{4};
+  SubscriptValue extent[]{5};
   whole.Establish(TypeCode{CFI_type_char}, sizeof buffer[0], &buffer, 1, extent,
       CFI_attribute_pointer);
   whole.Dump();
   whole.Check();
   Descriptor &section{staticDescriptor[1].descriptor()};
-  SubscriptValue lowers[]{0}, uppers[]{3}, strides[]{1};
+  SubscriptValue lowers[]{0}, uppers[]{4}, strides[]{1};
   section.Establish(whole.type(), whole.ElementBytes(), nullptr, 1, extent,
       CFI_attribute_pointer);
   if (auto error{
@@ -57,12 +57,16 @@
   }
   section.Dump();
   section.Check();
-  const char *format{"('?abcde,',T1,'>',T9,A,TL12,A,TR25,'<'//G0,25X,'done')"};
+  const char *format{
+      "('?abcde,',T1,'>',T9,A,TL12,A,TR25,'<'//G0,17X,'abcd',1(2I4))"};
   auto cookie{IONAME(BeginInternalArrayFormattedOutput)(
       section, format, std::strlen(format))};
   IONAME(OutputAscii)(cookie, "WORLD", 5);
   IONAME(OutputAscii)(cookie, "HELLO", 5);
   IONAME(OutputInteger64)(cookie, 789);
+  for (int j{666}; j <= 999; j += 111) {
+    IONAME(OutputInteger64)(cookie, j);
+  }
   if (auto status{IONAME(EndIoStatement)(cookie)}) {
     Fail() << "multiline: '" << format << "' failed, status "
            << static_cast<int>(status) << '\n';
@@ -70,7 +74,8 @@
     test(format,
         ">HELLO, WORLD                  <"
         "                                "
-        "789                         done"
+        "789                 abcd 666 777"
+        " 888 999                        "
         "                                ",
         std::string{buffer[0], sizeof buffer});
   }