diff --git a/simplecpp.cpp b/simplecpp.cpp
index 7afc17ab..dd73d6c7 100644
--- a/simplecpp.cpp
+++ b/simplecpp.cpp
@@ -67,6 +67,11 @@ static bool isOct(const std::string &s)
     return s.size()>1 && (s[0]=='0') && (s[1] >= '0') && (s[1] < '8');
 }
 
+static bool isBin(const std::string &s)
+{
+    return s.size()>2 && s.compare(0,2,"0b")==0;
+}
+
 static bool isStringLiteral(const std::string &s)
 {
     return s.size() > 1 && (s[0]=='\"') && (*s.rbegin()=='\"');
@@ -117,32 +122,51 @@ static std::string locstring(const simplecpp::Location &loc)
 }
 #endif
 
-static long long stringToLL(const std::string &s)
-{
-    long long ret;
-    const bool hex = isHex(s);
-    const bool oct = isOct(s);
-    std::istringstream istr(hex ? s.substr(2) : oct ? s.substr(1) : s);
-    if (hex)
-        istr >> std::hex;
-    else if (oct)
-        istr >> std::oct;
-    istr >> ret;
-    return ret;
+static unsigned long long stringToULL(const std::string &s, std::size_t offset = 0)
+{
+    unsigned long long base = 10;
+    if (isHex(s.substr(offset))) {
+        offset += 2;
+        base = 16;
+    } else if (isOct(s.substr(offset))) {
+        offset += 1;
+        base = 8;
+    } else if (isBin(s.substr(offset))) {
+        offset += 2;
+        base = 2;
+    }
+
+    unsigned long long result = 0;
+    for (std::size_t i = offset; i < s.size(); i++) {
+        const char c = s[i];
+        result *= base;
+
+        unsigned long long d;
+        if ('0' <= c && c <= '9') {
+            d = c - '0';
+        } else if ('a' <= c && c <= 'f') {
+            d = 10 + c - 'a';
+        } else if ('A' <= c && c <= 'F') {
+            d = 10 + c - 'A';
+        } else {
+            throw std::runtime_error("invalid integer literal");
+        }
+
+        if (d >= base) {
+            throw std::runtime_error("invalid integer literal");
+        }
+
+        result += d;
+    }
+
+    return result;
 }
 
-static unsigned long long stringToULL(const std::string &s)
+static long long stringToLL(const std::string &s)
 {
-    unsigned long long ret;
-    const bool hex = isHex(s);
-    const bool oct = isOct(s);
-    std::istringstream istr(hex ? s.substr(2) : oct ? s.substr(1) : s);
-    if (hex)
-        istr >> std::hex;
-    else if (oct)
-        istr >> std::oct;
-    istr >> ret;
-    return ret;
+    if (s.size() > 0 && s[0] == '-')
+        return -stringToULL(s, 1);
+    return stringToULL(s);
 }
 
 static bool endsWith(const std::string &s, const std::string &e)
diff --git a/test.cpp b/test.cpp
index fa94a266..bf9ee987 100644
--- a/test.cpp
+++ b/test.cpp
@@ -2046,6 +2046,52 @@ static void ifUndefFuncStyleMacro()
     ASSERT_EQUALS("file0,1,syntax_error,failed to evaluate #if condition, undefined function-like macro invocation: A( ... )\n", toString(outputList));
 }
 
+static void testIfIntegerLiteral(const std::string &value, const std::string &literal, bool expectError)
+{
+    const std::string code = "#define A " + value + "\n"
+                             "#if A == " + literal + "\n"
+                             "int x = " + literal + ";\n"
+                             "#endif\n";
+
+    simplecpp::OutputList outputList;
+
+    std::string literalPreprocessed = literal;
+    if (literalPreprocessed[0] == '-')
+    {
+        literalPreprocessed = "- " + literalPreprocessed.substr(1);
+    }
+
+    if (expectError) {
+        ASSERT_EQUALS("", preprocess(code.c_str(), &outputList));
+        ASSERT_EQUALS("file0,2,syntax_error,failed to evaluate #if condition, invalid integer literal\n", toString(outputList));
+    } else {
+        ASSERT_EQUALS("\n\nint x = " + literalPreprocessed + " ;", preprocess(code.c_str(), &outputList));
+        ASSERT_EQUALS("", toString(outputList));
+    }
+}
+
+static void ifIntegerLiteral()
+{
+    testIfIntegerLiteral("123", "123", false);
+    testIfIntegerLiteral("-123", "-123", false);
+
+    testIfIntegerLiteral("123", "0x7b", false);
+    testIfIntegerLiteral("-123", "-0x7b", false);
+
+    testIfIntegerLiteral("123", "0x7B", false);
+    testIfIntegerLiteral("-123", "-0x7B", false);
+
+    testIfIntegerLiteral("123", "0173", false);
+    testIfIntegerLiteral("-123", "-0173", false);
+
+    testIfIntegerLiteral("123", "0b1111011", false);
+    testIfIntegerLiteral("-123", "-0b1111011", false);
+
+    testIfIntegerLiteral("123", "0xGH", true);
+    testIfIntegerLiteral("123", "019", true);
+    testIfIntegerLiteral("123", "0b30", true);
+}
+
 static void location1()
 {
     const char *code;
@@ -3688,6 +3734,7 @@ int main(int argc, char **argv)
     TEST_CASE(ifalt); // using "and", "or", etc
     TEST_CASE(ifexpr);
     TEST_CASE(ifUndefFuncStyleMacro);
+    TEST_CASE(ifIntegerLiteral);
 
     TEST_CASE(location1);
     TEST_CASE(location2);