diff --git a/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java b/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java
index 6220133d98ee..e8acbb991e62 100644
--- a/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java
+++ b/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java
@@ -216,10 +216,16 @@ public abstract class CompatibilityVisitor extends PyAnnotator {
   public void visitPyStringLiteralExpression(final PyStringLiteralExpression node) {
     super.visitPyStringLiteralExpression(node);
 
+    boolean seenBytes = false;
+    boolean seenNonBytes = false;
     for (PyStringElement element : node.getStringElements()) {
       final String prefix = element.getPrefix().toUpperCase();
       if (prefix.isEmpty()) continue;
 
+      final boolean bytes = element.isBytes();
+      seenBytes |= bytes;
+      seenNonBytes |= !bytes;
+
       final int elementStart = element.getTextOffset();
       registerForAllMatchingVersions(level -> !getSupportedStringPrefixes(level).contains(prefix),
                                      " not support a '" + prefix + "' prefix",
@@ -228,6 +234,13 @@ public abstract class CompatibilityVisitor extends PyAnnotator {
                                      new RemovePrefixQuickFix(prefix),
                                      true);
     }
+
+    if (seenBytes && seenNonBytes) {
+      registerForAllMatchingVersions(LanguageLevel::isPy3K,
+                                     " not allow to mix bytes and non-bytes literals",
+                                     node,
+                                     null);
+    }
   }
 
   @NotNull
diff --git a/python/testData/highlighting/mixedBytesAndNonBytes.py b/python/testData/highlighting/mixedBytesAndNonBytes.py
new file mode 100644
index 000000000000..cb5389001d8e
--- /dev/null
+++ b/python/testData/highlighting/mixedBytesAndNonBytes.py
@@ -0,0 +1,3 @@
+<error descr="Python version 3.6 does not allow to mix bytes and non-bytes literals">b'qwe'u'asd'</error>
+<error descr="Python version 3.6 does not allow to mix bytes and non-bytes literals">b'qwe'r'asd'</error>
+<error descr="Python version 3.6 does not allow to mix bytes and non-bytes literals">b'qwe'f'asd'</error>
\ No newline at end of file
diff --git a/python/testData/inspections/PyCompatibilityInspection/stringLiteralExpression.py b/python/testData/inspections/PyCompatibilityInspection/stringLiteralExpression.py
index 8c2b46f5ee61..e36ebcc2df16 100644
--- a/python/testData/inspections/PyCompatibilityInspection/stringLiteralExpression.py
+++ b/python/testData/inspections/PyCompatibilityInspection/stringLiteralExpression.py
@@ -45,8 +45,10 @@ a = u""
 a = r""
 a = <warning descr="Python version 3.4, 3.5, 3.6, 3.7 do not support a 'UR' prefix">ur</warning>""
 
-# combined
-b = u"" b""
+# combined, PY-32321
+b = <warning descr="Python version 3.4, 3.5, 3.6, 3.7 do not allow to mix bytes and non-bytes literals">u"" b""</warning>
+b = <warning descr="Python version 3.4, 3.5, 3.6, 3.7 do not allow to mix bytes and non-bytes literals">r"" b""</warning>
+b = <warning descr="Python version 3.4, 3.5, 3.6, 3.7 do not allow to mix bytes and non-bytes literals">f"" b""</warning>
 
 # never was available
 a = <error descr="Python version 2.7 does not support a 'RR' prefix"><warning descr="Python version 2.6, 2.7, 3.4, 3.5, 3.6, 3.7 do not support a 'RR' prefix">rr</warning></error>""
diff --git a/python/testSrc/com/jetbrains/python/PythonHighlightingTest.java b/python/testSrc/com/jetbrains/python/PythonHighlightingTest.java
index 26f01065f8d1..333295c65d30 100644
--- a/python/testSrc/com/jetbrains/python/PythonHighlightingTest.java
+++ b/python/testSrc/com/jetbrains/python/PythonHighlightingTest.java
@@ -411,6 +411,11 @@ public class PythonHighlightingTest extends PyTestCase {
     doTest(LanguageLevel.PYTHON36, false, false);
   }
 
+  // PY-32321
+  public void testMixedBytesAndNonBytes() {
+    doTest(LanguageLevel.PYTHON36, false, false);
+  }
+
   @NotNull
   private static EditorColorsScheme createTemporaryColorScheme() {
     EditorColorsManager manager = EditorColorsManager.getInstance();