diff --git a/python/src/com/jetbrains/python/codeInsight/intentions/PyConvertToFStringIntention.java b/python/src/com/jetbrains/python/codeInsight/intentions/PyConvertToFStringIntention.java
index 2cb749e7991d..5d6bfa7256c8 100644
--- a/python/src/com/jetbrains/python/codeInsight/intentions/PyConvertToFStringIntention.java
+++ b/python/src/com/jetbrains/python/codeInsight/intentions/PyConvertToFStringIntention.java
@@ -355,7 +355,7 @@ public class PyConvertToFStringIntention extends PyBaseIntentionAction {
     if (adjusted == null) return false;
 
     newStringText.append(adjusted.getText());
-    final String quotedAttrsAndItems = quoteItemsInFragments(field, stringInfo.getSingleQuote());
+    final String quotedAttrsAndItems = quoteItemsInFragments(field, stringInfo);
     if (quotedAttrsAndItems == null) return false;
 
     newStringText.append(quotedAttrsAndItems);
@@ -396,7 +396,7 @@ public class PyConvertToFStringIntention extends PyBaseIntentionAction {
   }
 
   @Nullable
-  private static String quoteItemsInFragments(@NotNull PyNewStyleStringFormatParser.Field field, char hostStringQuote) {
+  private static String quoteItemsInFragments(@NotNull PyNewStyleStringFormatParser.Field field, @NotNull StringNodeInfo hostStringInfo) {
     List<String> escaped = new ArrayList<>();
     for (String part : field.getAttributesAndLookups()) {
       if (part.startsWith(".")) {
@@ -411,11 +411,17 @@ public class PyConvertToFStringIntention extends PyBaseIntentionAction {
           escaped.add(part);
           continue;
         }
-        final char quote = flipQuote(hostStringQuote);
-        if (indexText.indexOf(hostStringQuote) >= 0 || indexText.indexOf(quote) >= 0) {
-          return null;
+        final char originalQuote = hostStringInfo.getSingleQuote();
+        char targetQuote = flipQuote(originalQuote);
+        // there are no escapes inside the fragment, so the lookup key cannot contain 
+        // the host string quote unless it's a multiline string literal
+        if (indexText.indexOf(targetQuote) >= 0) {
+          if (!hostStringInfo.isTripleQuoted() || indexText.indexOf(originalQuote) >= 0) {
+            return null;
+          }
+          targetQuote = originalQuote;
         }
-        escaped.add("[" + quote + indexText + quote + "]");
+        escaped.add("[" + targetQuote + indexText + targetQuote + "]");
       }
     }
     return StringUtil.join(escaped, "");
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsAlternativeQuoteOfMultilineHost.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsAlternativeQuoteOfMultilineHost.py
new file mode 100644
index 000000000000..2230678e2739
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsAlternativeQuoteOfMultilineHost.py
@@ -0,0 +1 @@
+'''{x["]}'''.format(x=d)
\ No newline at end of file
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsAlternativeQuoteOfMultilineHost_after.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsAlternativeQuoteOfMultilineHost_after.py
new file mode 100644
index 000000000000..ea7492d0def3
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsAlternativeQuoteOfMultilineHost_after.py
@@ -0,0 +1 @@
+f'''{d['"']}'''
\ No newline at end of file
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost.py
new file mode 100644
index 000000000000..24d9a96c7e2a
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost.py
@@ -0,0 +1,3 @@
+'''
+{0["']}
+'''.format(d)
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost_after.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost_after.py
new file mode 100644
index 000000000000..24d9a96c7e2a
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost_after.py
@@ -0,0 +1,3 @@
+'''
+{0["']}
+'''.format(d)
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsQuoteOfMultilineHost.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsQuoteOfMultilineHost.py
new file mode 100644
index 000000000000..cc73e2551017
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsQuoteOfMultilineHost.py
@@ -0,0 +1 @@
+'''{x[']}'''.format(x=d)
\ No newline at end of file
diff --git a/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsQuoteOfMultilineHost_after.py b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsQuoteOfMultilineHost_after.py
new file mode 100644
index 000000000000..2de3590e84a5
--- /dev/null
+++ b/python/testData/intentions/PyConvertToFStringIntentionTest/formatMethodIndexContainsQuoteOfMultilineHost_after.py
@@ -0,0 +1 @@
+f'''{d["'"]}'''
\ No newline at end of file
diff --git a/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java b/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java
index 5d7e74d144c6..f01e6ba2eb06 100644
--- a/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java
+++ b/python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java
@@ -94,11 +94,27 @@ public class PyConvertToFStringIntentionTest extends PyIntentionTestCase {
   public void testFormatMethodItemAccess() {
     doTest();
   }
-
+  
+  // PY-21245
   public void testFormatMethodIndexContainsHostAlternativeQuote() {
     doTest();
   }
   
+  // PY-21245
+  public void testFormatMethodIndexContainsQuoteOfMultilineHost() {
+    doTest();    
+  }
+  
+  // PY-21245
+  public void testFormatMethodIndexContainsAlternativeQuoteOfMultilineHost() {
+    doTest();    
+  }
+
+  // PY-21245
+  public void testFormatMethodIndexContainsBothTypesOfQuotesInsideMultilineHost() {
+    doTest();
+  }
+
   public void testFormatMethodIndexContainsBackslash() {
     doTest();
   }