diff --git a/python/src/com/jetbrains/python/parsing/ExpressionParsing.java b/python/src/com/jetbrains/python/parsing/ExpressionParsing.java
index 82295f3a2ec0..840ee50100ef 100644
--- a/python/src/com/jetbrains/python/parsing/ExpressionParsing.java
+++ b/python/src/com/jetbrains/python/parsing/ExpressionParsing.java
@@ -305,7 +305,8 @@ public class ExpressionParsing extends Parsing {
       else {
         final PsiBuilder.Marker err = myBuilder.mark();
         boolean empty = true;
-        while (myBuilder.getTokenType() != PyTokenTypes.RPAR &&
+        while (!myBuilder.eof() &&
+               myBuilder.getTokenType() != PyTokenTypes.RPAR &&
                myBuilder.getTokenType() != PyTokenTypes.LINE_BREAK &&
                myBuilder.getTokenType() != PyTokenTypes.STATEMENT_BREAK) {
           myBuilder.advanceLexer();
diff --git a/python/testData/editing/incompleteFunctionTypeComment.after.py b/python/testData/editing/incompleteFunctionTypeComment.after.py
new file mode 100644
index 000000000000..9a8b67f50f3b
--- /dev/null
+++ b/python/testData/editing/incompleteFunctionTypeComment.after.py
@@ -0,0 +1,2 @@
+def foo(bar):
+    # type: (foo.
\ No newline at end of file
diff --git a/python/testData/editing/incompleteFunctionTypeComment.py b/python/testData/editing/incompleteFunctionTypeComment.py
new file mode 100644
index 000000000000..61e719eda496
--- /dev/null
+++ b/python/testData/editing/incompleteFunctionTypeComment.py
@@ -0,0 +1,2 @@
+def foo(bar):
+    # type: (foo<caret>
\ No newline at end of file
diff --git a/python/testSrc/com/jetbrains/python/PyEditingTest.java b/python/testSrc/com/jetbrains/python/PyEditingTest.java
index 979e634efe2b..d7efb2165734 100644
--- a/python/testSrc/com/jetbrains/python/PyEditingTest.java
+++ b/python/testSrc/com/jetbrains/python/PyEditingTest.java
@@ -591,4 +591,9 @@ public class PyEditingTest extends PyTestCase {
                 "    return bar, 'so' \\\n" +
                 "                'me'");
   }
+
+  // PY-27178
+  public void testIncompleteFunctionTypeComment() {
+    doTypingTest('.');
+  }
 }