diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 94f0f0328..6b09411f2 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -3297,7 +3297,7 @@ void Tokenizer::setVarId()
 
 
 // Variable declarations can't start with "return" etc.
-#define NOTSTART_C "case", "default", "goto", "NOT", "return", "sizeof", "typedef"
+#define NOTSTART_C "NOT", "case", "default", "goto", "not", "return", "sizeof", "typedef"
 static const std::set<std::string> notstart_c = { NOTSTART_C };
 static const std::set<std::string> notstart_cpp = { NOTSTART_C,
                                                     "delete", "friend", "new", "throw", "using", "virtual", "explicit", "const_cast", "dynamic_cast", "reinterpret_cast", "static_cast", "template"
diff --git a/test/testvarid.cpp b/test/testvarid.cpp
index ba3bb6318..b3a1a6e47 100644
--- a/test/testvarid.cpp
+++ b/test/testvarid.cpp
@@ -167,8 +167,8 @@ private:
         TEST_CASE(varid_trailing_return1); // #8889
         TEST_CASE(varid_trailing_return2); // #9066
         TEST_CASE(varid_parameter_pack); // #9383
-
         TEST_CASE(varid_for_auto_cpp17);
+        TEST_CASE(varid_not); // #9689 'not x'
 
         TEST_CASE(varidclass1);
         TEST_CASE(varidclass2);
@@ -2598,6 +2598,16 @@ private:
         ASSERT_EQUALS(exp1, tokenize(code));
     }
 
+    void varid_not() { // #9689 'not x'
+        const char code1[] = "void foo(int x) const {\n"
+                             "  if (not x) {}\n"
+                             "}";
+        const char exp1[] = "1: void foo ( int x@1 ) const {\n"
+                            "2: if ( not x@1 ) { }\n"
+                            "3: }\n";
+        ASSERT_EQUALS(exp1, tokenize(code1));
+    }
+
     void varidclass1() {
         const std::string actual = tokenize(
                                        "class Fred\n"