diff --git a/src/Base64.cc b/src/Base64.cc
index ed45c513ed..03bd22e9cc 100644
--- a/src/Base64.cc
+++ b/src/Base64.cc
@@ -5,9 +5,9 @@
 int Base64Converter::default_base64_table[256];
 const string Base64Converter::default_alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
-void Base64Converter::Encode(int len, const unsigned char* data, int* pblen, char** pbuf)
+void Base64Converter::Encode(size_t len, const unsigned char* data, size_t* pblen, char** pbuf)
 	{
-	int blen;
+	size_t blen;
 	char *buf;
 
 	if ( ! pbuf )
@@ -23,12 +23,12 @@ void Base64Converter::Encode(int len, const unsigned char* data, int* pblen, cha
 		}
 	else
 		{
-		blen = (int)(4 * ceil((double)len / 3));
+		blen = (size_t)(4 * ceil((double)len / 3));
 		*pbuf = buf = new char[blen];
 		*pblen = blen;
 		}
 
-	for ( int i = 0, j = 0; (i < len) && ( j < blen ); )
+	for ( size_t i = 0, j = 0; (i < len) && ( j < blen ); )
 		{
 			uint32_t bit32 = data[i++]  << 16;
 			bit32 += (i++ < len ? data[i-1] : 0) << 8; 
@@ -107,9 +107,9 @@ Base64Converter::~Base64Converter()
 		delete [] base64_table;
 	}
 
-int Base64Converter::Decode(int len, const char* data, int* pblen, char** pbuf)
+size_t Base64Converter::Decode(size_t len, const char* data, size_t* pblen, char** pbuf)
 	{
-	int blen;
+	size_t blen;
 	char* buf;
 
 	// Initialization of table on first_time call of Decode.
@@ -128,11 +128,11 @@ int Base64Converter::Decode(int len, const char* data, int* pblen, char** pbuf)
 		{
 		// Estimate the maximal number of 3-byte groups needed,
 		// plus 1 byte for the optional ending NUL.
-		blen = int((len + base64_group_next + 3) / 4) * 3 + 1;
+		blen = size_t((len + base64_group_next + 3) / 4) * 3 + 1;
 		*pbuf = buf = new char[blen];
 		}
 
-	int dlen = 0;
+	size_t dlen = 0;
 
 	while ( 1 )
 		{
@@ -183,7 +183,7 @@ int Base64Converter::Decode(int len, const char* data, int* pblen, char** pbuf)
 
 		int k = base64_table[(unsigned char) data[dlen]];
 		if ( k >= 0 )
-			base64_group[base64_group_next++] = k;
+			base64_group[base64_group_next++] = static_cast<char> (k);
 		else
 			{
 			if ( ++errored == 1 )
@@ -197,7 +197,7 @@ int Base64Converter::Decode(int len, const char* data, int* pblen, char** pbuf)
 	return dlen;
 	}
 
-int Base64Converter::Done(int* pblen, char** pbuf)
+int Base64Converter::Done(size_t* pblen, char** pbuf)
 	{
 	const char* padding = "===";
 
@@ -225,8 +225,8 @@ BroString* decode_base64(const BroString* s, const BroString* a, Connection* con
 		return 0;
 		}
 
-	int buf_len = int((s->Len() + 3) / 4) * 3 + 1;
-	int rlen2, rlen = buf_len;
+	size_t buf_len = size_t((s->Len() + 3) / 4) * 3 + 1;
+	size_t rlen2, rlen = buf_len;
 	char* rbuf2, *rbuf = new char[rlen];
 
 	Base64Converter dec(conn, a ? a->CheckString() : "");
@@ -258,7 +258,7 @@ BroString* encode_base64(const BroString* s, const BroString* a, Connection* con
 		}
 
 	char* outbuf = 0;
-	int outlen = 0;
+	size_t outlen = 0;
 	Base64Converter enc(conn, a ? a->CheckString() : "");
 	enc.Encode(s->Len(), (const unsigned char*) s->Bytes(), &outlen, &outbuf);
 
diff --git a/src/Base64.h b/src/Base64.h
index 8c8146c3c0..60bfa8269e 100644
--- a/src/Base64.h
+++ b/src/Base64.h
@@ -1,4 +1,5 @@
-#pragma once
+#ifndef base64_h
+#define base64_h
 
 #include <assert.h>
 #include <stdio.h>
@@ -30,10 +31,10 @@ public:
 	// input bytes processed, since the decoding will stop when there
 	// is not enough output buffer space.
 
-	int Decode(int len, const char* data, int* blen, char** buf);
-	void Encode(int len, const unsigned char* data, int* blen, char** buf);
+	size_t Decode(size_t len, const char* data, size_t* pblen, char** buf);
+	void Encode(size_t len, const unsigned char* data, size_t* blen, char** buf);
 
-	int Done(int* pblen, char** pbuf);
+	int Done(size_t* pblen, char** pbuf);
 	int HasData() const { return base64_group_next != 0; }
 
 	// True if an error has occurred.
@@ -70,3 +71,5 @@ protected:
 
 BroString* decode_base64(const BroString* s, const BroString* a = 0, Connection* conn = 0);
 BroString* encode_base64(const BroString* s, const BroString* a = 0, Connection* conn = 0);
+
+#endif /* base64_h */
diff --git a/src/analyzer/protocol/mime/MIME.cc b/src/analyzer/protocol/mime/MIME.cc
index b62dc11633..e3f6eac21d 100644
--- a/src/analyzer/protocol/mime/MIME.cc
+++ b/src/analyzer/protocol/mime/MIME.cc
@@ -1131,7 +1131,8 @@ void MIME_Entity::DecodeBase64(int len, const char* data)
 		{
 		rlen = 128;
 		char* prbuf = rbuf;
-		int decoded = base64_decoder->Decode(len, data, &rlen, &prbuf);
+		size_t x = static_cast<size_t> (rlen);
+		int decoded = base64_decoder->Decode(len, data, &x, &prbuf); // typecasting for now
 		DataOctets(rlen, rbuf);
 		len -= decoded; data += decoded;
 		}
@@ -1164,8 +1165,8 @@ void MIME_Entity::FinishDecodeBase64()
 	int rlen = 128;
 	char rbuf[128];
 	char* prbuf = rbuf;
-
-	if ( base64_decoder->Done(&rlen, &prbuf) )
+	size_t x = static_cast<size_t> (rlen); 
+	if ( base64_decoder->Done(&x, &prbuf) ) // typecasting for now
 		{ // some remaining data
 		if ( rlen > 0 )
 			DataOctets(rlen, rbuf);