diff --git a/simplecpp.cpp b/simplecpp.cpp
index 48a7ce9e..219a3079 100644
--- a/simplecpp.cpp
+++ b/simplecpp.cpp
@@ -206,11 +206,23 @@ static bool isAlternativeBinaryOp(const simplecpp::Token *tok, const std::string
             (isValue(tok->next) || tok->next->name || tok->next->op == '('));
 }
 
+static bool isAlternativeOpName(const simplecpp::Token *tok)
+{
+    static const std::set<std::string> altop{"and","or","bitand","bitor","compl","not","not_eq","xor"};
+    return tok->name && altop.find(tok->str()) != altop.end();
+}
+
 static bool isAlternativeUnaryOp(const simplecpp::Token *tok, const std::string &alt)
 {
-    return ((tok->name && tok->str() == alt) &&
-            (!tok->previous || tok->previous->op == '(') &&
-            (tok->next && (tok->next->name || tok->next->number)));
+    if (!tok->name || tok->str() != alt)
+        return false;
+    // a unary operator comes first or after another operator, but not after an operand
+    const simplecpp::Token * const prev = tok->previous;
+    if (prev && (isValue(prev) || prev->op == ')' || (prev->name && !isAlternativeOpName(prev))))
+        return false;
+    // it is followed by the start of an operand
+    const simplecpp::Token * const next = tok->next;
+    return next && (next->name || isValue(next) || next->isOneOf("(!~+-"));
 }
 
 static std::string replaceAll(std::string s, const std::string& from, const std::string& to)
@@ -1318,7 +1330,7 @@ void simplecpp::TokenList::constFoldUnaryNotPosNeg(simplecpp::Token *tok1)
             tok->setstr(toString(~stringToLL(tok->next->str())));
             deleteToken(tok->next);
         } else {
-            if (tok->previous && (isValue(tok->previous) || tok->previous->name))
+            if (tok->previous && (isValue(tok->previous) || (tok->previous->name && !isAlternativeOpName(tok->previous))))
                 continue;
             if (!isValue(tok->next))
                 continue;
@@ -2992,8 +3004,7 @@ static void simplifyName(simplecpp::TokenList &expr, const simplecpp::DUI &dui)
                 tok->setstr(tok->str() == "true" ? "1" : "0");
                 continue;
             }
-            static const std::set<std::string> altop{"and","or","bitand","bitor","compl","not","not_eq","xor"};
-            if (altop.find(tok->str()) != altop.end()) {
+            if (isAlternativeOpName(tok)) {
                 bool alt;
                 if (tok->str() == "not" || tok->str() == "compl") {
                     alt = isAlternativeUnaryOp(tok,tok->str());
diff --git a/test.cpp b/test.cpp
index 866af490..9b30794b 100644
--- a/test.cpp
+++ b/test.cpp
@@ -2869,7 +2869,10 @@ static void ifShortCircuit()
         "defined(X) and X/0",
         "0 && 1 bitor (1/0)",
         "!(1 || (1/0) bitand 1)",
-        "0 and 1 xor (1/0)"
+        "0 and 1 xor (1/0)",
+        "0 && not (1/0)",
+        "0 && compl (1/0)",
+        "!(1 || not not (1/0))"
     };
     for (const char * const expr : exprs) {
         const std::string code = std::string("#if ") + expr + "\n"
@@ -2886,6 +2889,9 @@ static void ifShortCircuit()
     simplecpp::OutputList outputList;
     ASSERT_EQUALS("", preprocess("#if 1 && (1/0)\n#endif\n", &outputList));
     ASSERT_EQUALS("file0,1,syntax_error,failed to evaluate #if condition, division/modulo by zero\n", toString(outputList));
+    outputList.clear();
+    ASSERT_EQUALS("", preprocess("#if not (1/0)\n#endif\n", &outputList));
+    ASSERT_EQUALS("file0,1,syntax_error,failed to evaluate #if condition, division/modulo by zero\n", toString(outputList));
 }
 
 static void ifZeroCondition()
@@ -3022,6 +3028,45 @@ static void ifalt()   // using "and", "or", etc
     ASSERT_EQUALS("\n1", preprocess(code));
 }
 
+static void ifAltUnaryOperators()   // "not" and "compl" anywhere a unary operator is allowed
+{
+    const char * const exprs[] = {
+        // at the start of the expression
+        "not 0",
+        "(not 0)",
+        "not 0 && 1",
+        "compl 0",
+        // after a binary operator, "?" or ":"
+        "1 && not 0",
+        "1 and not 0",
+        "0 || not 0",
+        "1 == not 0",
+        "0 ? 0 : not 0",
+        "1 ? not 0 : 0",
+        // next to another unary operator
+        "not not 1",
+        "not -0",
+        "not ~-1",
+        "not !0 == 0",
+        "compl compl 1 == 1",
+        "compl -1 == 0",
+        "!(compl -1 + 1 == 0)",
+        "-compl 0 == 1",
+        // followed by "("
+        "not (0)",
+        "not(0)",
+        "compl (0) == -1"
+    };
+    for (const char * const expr : exprs) {
+        const std::string code = std::string("#if ") + expr + "\n"
+                                 "1\n"
+                                 "#else\n"
+                                 "2\n"
+                                 "#endif\n";
+        ASSERT_EQUALS("\n1", preprocess(code.c_str()));
+    }
+}
+
 static void ifexpr()
 {
     const char code[] = "#define MACRO()  (1)\n"
@@ -5226,6 +5271,7 @@ static void runTests(int argc, char **argv, Input input)
     TEST_CASE(ifInvalidExpression);
     TEST_CASE(ifTrueFalse);
     TEST_CASE(ifalt); // using "and", "or", etc
+    TEST_CASE(ifAltUnaryOperators);
     TEST_CASE(ifexpr);
     TEST_CASE(ifUndefFuncStyleMacro);