diff --git a/lib/checkbufferoverrun.cpp b/lib/checkbufferoverrun.cpp
index 30b63ba39..723879c98 100644
--- a/lib/checkbufferoverrun.cpp
+++ b/lib/checkbufferoverrun.cpp
@@ -1279,7 +1279,7 @@ void CheckBufferOverrun::checkGlobalAndLocalVariable()
     for (const Token *tok = _tokenizer->tokens(); tok; tok = tok->next()) {
         if (Token::Match(tok, "%str% [ %num% ]")) {
             std::string str = tok->strValue();
-            std::size_t index = std::atoi(tok->strAt(2).c_str());
+            std::size_t index = (std::size_t)std::atoi(tok->strAt(2).c_str());
             if (index > str.length()) {
                 bufferOverrunError(tok, tok->str());
             }
diff --git a/lib/checknullpointer.cpp b/lib/checknullpointer.cpp
index 48422adbd..e6cbcc9d0 100644
--- a/lib/checknullpointer.cpp
+++ b/lib/checknullpointer.cpp
@@ -377,7 +377,7 @@ bool CheckNullPointer::CanFunctionAssignPointer(const Token *functiontoken, unsi
     if (Token::Match(functiontoken, "if|while|for|switch|sizeof|catch"))
         return false;
 
-    int argumentNumber = 0;
+    unsigned int argumentNumber = 0;
     for (const Token *arg = functiontoken->tokAt(2); arg; arg = arg->nextArgument()) {
         if (Token::Match(arg, "%varid% [,)]", varid)) {
             const Function* func = _tokenizer->getSymbolDatabase()->findFunctionByName(functiontoken->str(), functiontoken->scope());
diff --git a/lib/preprocessor.cpp b/lib/preprocessor.cpp
index 3c6ae34eb..d5f897e45 100644
--- a/lib/preprocessor.cpp
+++ b/lib/preprocessor.cpp
@@ -128,9 +128,9 @@ std::string Preprocessor::read(std::istream &istr, const std::string &filename)
     // The UTF-16 BOM is 0xfffe or 0xfeff.
     unsigned int bom = 0;
     if (istr.peek() >= 0xfe) {
-        bom = (istr.get() << 8);
+        bom = ((unsigned int)istr.get() << 8);
         if (istr.peek() >= 0xfe)
-            bom |= istr.get();
+            bom |= (unsigned int)istr.get();
     }
 
     // ------------------------------------------------------------------------------------------