diff --git a/python/src/com/jetbrains/python/inspections/PyNewStyleStringFormatParser.java b/python/src/com/jetbrains/python/inspections/PyNewStyleStringFormatParser.java
index 0ab8b22e21c5..4b0049255781 100644
--- a/python/src/com/jetbrains/python/inspections/PyNewStyleStringFormatParser.java
+++ b/python/src/com/jetbrains/python/inspections/PyNewStyleStringFormatParser.java
@@ -117,6 +117,8 @@ public class PyNewStyleStringFormatParser {
   private Field parseField(int startOffset, int recursionDepth) {
     assert myNodeText.charAt(startOffset) == '{';
 
+    int autoFieldNumber = myImplicitlyNumberedFieldsCounter;
+
     // in the order of appearance inside a field
     final TIntArrayList attrAndLookupBounds = new TIntArrayList();
     int conversionStart = -1;
@@ -155,6 +157,11 @@ public class PyNewStyleStringFormatParser {
           if (!recovering) {
             // avoid duplicate offsets in sequences like "]." or "]["
             addIfNotLastItem(attrAndLookupBounds, offset);
+            
+            // no name in the field, increment implicitly named fields counter
+            if (attrAndLookupBounds.size() == 1 && attrAndLookupBounds.get(0) == startOffset + 1) {
+              myImplicitlyNumberedFieldsCounter++;
+            }
           }
 
           if (c == ':') {
@@ -194,23 +201,18 @@ public class PyNewStyleStringFormatParser {
       addIfNotLastItem(attrAndLookupBounds, contentEnd);
     }
 
-
-    final Field field = new Field(myNodeText,
-                                  startOffset,
-                                  attrAndLookupBounds.toNativeArray(),
-                                  conversionStart,
-                                  formatSpecStart,
-                                  nestedFields,
-                                  rightBraceOffset,
-                                  rightBraceOffset == -1 ? contentEnd : rightBraceOffset + 1,
-                                  myImplicitlyNumberedFieldsCounter,
-                                  recursionDepth);
-
     assert !attrAndLookupBounds.isEmpty();
-    if (attrAndLookupBounds.get(0) == startOffset + 1) {
-      myImplicitlyNumberedFieldsCounter++;
-    }
-    return field;
+
+    return new Field(myNodeText,
+                     startOffset,
+                     attrAndLookupBounds.toNativeArray(),
+                     conversionStart,
+                     formatSpecStart,
+                     nestedFields,
+                     rightBraceOffset,
+                     rightBraceOffset == -1 ? contentEnd : rightBraceOffset + 1,
+                     autoFieldNumber,
+                     recursionDepth);
   }
 
   private static void addIfNotLastItem(TIntArrayList attrAndLookupBounds, int offset) {
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodNestedFields3.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodNestedFields3.py
new file mode 100644
index 000000000000..e934c6fa94d0
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodNestedFields3.py
@@ -0,0 +1 @@
+'{:.{}}'.format(3.1415926, 3)
\ No newline at end of file
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodNestedFields3_after.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodNestedFields3_after.py
new file mode 100644
index 000000000000..7329a20ac086
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodNestedFields3_after.py
@@ -0,0 +1 @@
+f'{3.1415926:.{3}}'
\ No newline at end of file
diff --git a/python/testSrc/com/jetbrains/python/PyStringFormatParserTest.java b/python/testSrc/com/jetbrains/python/PyStringFormatParserTest.java
index 1bf3e1968d00..ce177548de2e 100644
--- a/python/testSrc/com/jetbrains/python/PyStringFormatParserTest.java
+++ b/python/testSrc/com/jetbrains/python/PyStringFormatParserTest.java
@@ -178,8 +178,8 @@ public class PyStringFormatParserTest extends UsefulTestCase {
     final List<Field> topLevelFields = result.getFields();
     assertSize(2, topLevelFields);
     assertSize(5, result.getAllFields());
-    assertSameElements(result.getAllFields().stream().map(f -> f.getDepth()).toArray(), 1, 2, 3, 4, 1);
-    assertSameElements(result.getAllFields().stream().map(f -> f.getAutoPosition()).toArray(), 0, 1, 2, 3, 4);
+    assertOrderedEquals(result.getAllFields().stream().map(f -> f.getDepth()).toArray(), 1, 2, 3, 4, 1);
+    assertOrderedEquals(result.getAllFields().stream().map(f -> f.getAutoPosition()).toArray(), 0, 1, 2, 3, 4);
   }
 
   public void testNewStyleAttrAndLookups() {
@@ -195,40 +195,40 @@ public class PyStringFormatParserTest extends UsefulTestCase {
 
     field = doParseAndGetFirstField("u'{foo.bar.baz}'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), ".bar", ".baz");
+    assertOrderedEquals(field.getAttributesAndLookups(), ".bar", ".baz");
 
     field = doParseAndGetFirstField("u'{foo[bar][baz]}'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), "[bar]", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[bar]", "[baz]");
 
     field = doParseAndGetFirstField("u'{foo.bar[baz]}'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), ".bar", "[baz]");
 
     field = doParseAndGetFirstField("u'{foo.bar[baz}'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), ".bar");
 
     field = doParseAndGetFirstField("u'{foo[{bar[baz]}'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), "[{bar[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[{bar[baz]");
 
     field = doParseAndGetFirstField("u'{foo[{} {0} {bar.baz}]'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), "[{} {0} {bar.baz}]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[{} {0} {bar.baz}]");
 
     field = doParseAndGetFirstField("u'{foo[bar]baz'");
     assertEquals("foo", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), "[bar]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[bar]");
 
     field = doParseAndGetFirstField("'{0[foo][.!:][}]}'");
     assertEquals("0", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", "[.!:]", "[}]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", "[.!:]", "[}]");
 
     field = doParseAndGetFirstField("'{.foo.bar}'");
     assertEmpty(field.getFirstName());
     assertEquals(TextRange.create(2, 2), field.getFirstNameRange());
-    assertSameElements(field.getAttributesAndLookups(), ".foo", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), ".foo", ".bar");
 
     field = doParseAndGetFirstField("'{}'");
     assertEmpty(field.getFirstName());
@@ -261,68 +261,68 @@ public class PyStringFormatParserTest extends UsefulTestCase {
     assertEmpty(field.getAttributesAndLookups());
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     // do not recover unfinished lookups
     field = doParseAndGetFirstField("'{0[foo].bar[ba}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     field = doParseAndGetFirstField("'{0[foo].bar[ba!}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     field = doParseAndGetFirstField("'{0[foo].bar[ba:}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     field = doParseAndGetFirstField("'{0[foo].bar[ba'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     field = doParseAndGetFirstField("'{0[foo].bar[ba");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     // do not recover illegal attributes
     field = doParseAndGetFirstField("'{0[foo].bar[baz]quux}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]quux!}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]quux:}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]quux'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0[foo].bar[baz]quux");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar", "[baz]");
 
     field = doParseAndGetFirstField("'{0..}'");
     assertEquals("0", field.getFirstName());
-    assertSameElements(field.getAttributesAndLookups(), ".", ".");
+    assertOrderedEquals(field.getAttributesAndLookups(), ".", ".");
 
     // recover attributes
     field = doParseAndGetFirstField("'{0[foo].}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".");
 
     field = doParseAndGetFirstField("'{0[foo].'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".");
 
     field = doParseAndGetFirstField("'{0[foo].");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".");
 
     field = doParseAndGetFirstField("'{0[foo].bar}'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     field = doParseAndGetFirstField("'{0[foo].bar'");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
 
     field = doParseAndGetFirstField("'{0[foo].bar");
-    assertSameElements(field.getAttributesAndLookups(), "[foo]", ".bar");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[foo]", ".bar");
   }
 
   public void testAutoPosition() {
@@ -361,12 +361,12 @@ public class PyStringFormatParserTest extends UsefulTestCase {
 
   public void testNewStyleNamedUnicodeEscapeInLookup() {
     final Field field = doParseAndGetFirstField("'{foo[\\N{ESCAPE WITH ]}]}'");
-    assertSameElements(field.getAttributesAndLookups(), "[\\N{ESCAPE WITH ]}]");
+    assertOrderedEquals(field.getAttributesAndLookups(), "[\\N{ESCAPE WITH ]}]");
   }
 
   public void testNewStyleNamedUnicodeEscapeInAttribute() {
     final Field field = doParseAndGetFirstField("'{foo.b\\N{ESCAPE WITH [}.b\\N{ESCAPE WITH .}}'");
-    assertSameElements(field.getAttributesAndLookups(), ".b\\N{ESCAPE WITH [}", ".b\\N{ESCAPE WITH .}");
+    assertOrderedEquals(field.getAttributesAndLookups(), ".b\\N{ESCAPE WITH [}", ".b\\N{ESCAPE WITH .}");
   }
 
   public void testNewStyleUnclosedLookupEndsWithRightBrace() {
diff --git a/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java b/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java
index 71b67a9425ba..7d1f2528a489 100644
--- a/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java
+++ b/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java
@@ -158,4 +158,9 @@ public class PyConvertToFStringIntentionTest extends PyIntentionTestCase {
   public void testFormatMethodNestedFields2() {
     doTest();
   }
+
+  // PY-21244
+  public void testFormatMethodNestedFields3() {
+    doTest();
+  }
 }