2 files changed, 8 insertions, 1 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java b/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
index 15283f8a71..e5805f5bc0 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Lexer.java
@@ -252,7 +252,8 @@ public final class Lexer {
       } else if (c == '\r') {
         pos++;
       } else if (c == '\t') {
-        indentLen += 8 - indentLen % 8;
+        error("Tabulations are not allowed for identation. Use spaces instead.");
+        indentLen++;
         pos++;
       } else if (c == '\n') { // entirely blank line: discard
         indentLen = 0;
diff --git a/src/test/java/com/google/devtools/build/lib/syntax/LexerTest.java b/src/test/java/com/google/devtools/build/lib/syntax/LexerTest.java
index 0fd91df959..0417074abc 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/LexerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/LexerTest.java
@@ -356,6 +356,12 @@ public class LexerTest {
   }
 
   @Test
+  public void testIndentationWithTab() throws Exception {
+    tokens("def x():\n\tpass");
+    assertThat(lastError.toString()).contains("Tabulations are not allowed");
+  }
+
+  @Test
   public void testIndentationWithCrLf() throws Exception {
     assertThat(values(tokens("1\r\n  2\r\n")))
         .isEqualTo("INT(1) NEWLINE INDENT INT(2) NEWLINE OUTDENT NEWLINE EOF");