diff --git a/src/common.h b/src/common.h
index ca203ee5c..e3a9e1984 100644
--- a/src/common.h
+++ b/src/common.h
@@ -33,14 +33,14 @@
 #	include "win32/pthread.h"
 #endif
 
-# define snprintf _snprintf
-
 #else
-# include <unistd.h>
 
+# include <unistd.h>
 # ifdef GIT_THREADS
 #	include <pthread.h>
 # endif
+#define GIT_STDLIB_CALL
+
 #endif
 
 #include "git2/types.h"
diff --git a/src/hashsig.c b/src/hashsig.c
index 60649fd11..e9c5164a4 100644
--- a/src/hashsig.c
+++ b/src/hashsig.c
@@ -19,7 +19,7 @@ typedef uint64_t hashsig_state;
 
 #define HASHSIG_HEAP_SIZE ((1 << 7) - 1)
 
-typedef int (*hashsig_cmp)(const void *a, const void *b);
+typedef int (GIT_STDLIB_CALL *hashsig_cmp)(const void *a, const void *b);
 
 typedef struct {
 	int size, asize;
@@ -53,13 +53,13 @@ static void hashsig_heap_init(hashsig_heap *h, hashsig_cmp cmp)
 	h->cmp   = cmp;
 }
 
-static int hashsig_cmp_max(const void *a, const void *b)
+static int GIT_STDLIB_CALL hashsig_cmp_max(const void *a, const void *b)
 {
 	hashsig_t av = *(const hashsig_t *)a, bv = *(const hashsig_t *)b;
 	return (av < bv) ? -1 : (av > bv) ? 1 : 0;
 }
 
-static int hashsig_cmp_min(const void *a, const void *b)
+static int GIT_STDLIB_CALL hashsig_cmp_min(const void *a, const void *b)
 {
 	hashsig_t av = *(const hashsig_t *)a, bv = *(const hashsig_t *)b;
 	return (av > bv) ? -1 : (av < bv) ? 1 : 0;
@@ -183,8 +183,8 @@ static void hashsig_initial_window(
 	/* insert initial hash if we just finished */
 
 	if (win_len == HASHSIG_HASH_WINDOW) {
-		hashsig_heap_insert(&sig->mins, state);
-		hashsig_heap_insert(&sig->maxs, state);
+		hashsig_heap_insert(&sig->mins, (hashsig_t)state);
+		hashsig_heap_insert(&sig->maxs, (hashsig_t)state);
 		sig->considered = 1;
 	}
 
@@ -224,8 +224,8 @@ static int hashsig_add_hashes(
 		state = (state * HASHSIG_HASH_SHIFT) & HASHSIG_HASH_MASK;
 		state = (state + ch) & HASHSIG_HASH_MASK;
 
-		hashsig_heap_insert(&sig->mins, state);
-		hashsig_heap_insert(&sig->maxs, state);
+		hashsig_heap_insert(&sig->mins, (hashsig_t)state);
+		hashsig_heap_insert(&sig->maxs, (hashsig_t)state);
 		sig->considered++;
 
 		prog->window[prog->win_pos] = ch;
@@ -307,7 +307,7 @@ int git_hashsig_create_fromfile(
 
 	while (!error) {
 		if ((buflen = p_read(fd, buf, sizeof(buf))) <= 0) {
-			if ((error = buflen) < 0)
+			if ((error = (int)buflen) < 0)
 				giterr_set(GITERR_OS,
 					"Read error on '%s' calculating similarity hashes", path);
 			break;
diff --git a/src/win32/msvc-compat.h b/src/win32/msvc-compat.h
index 714a85e21..50865ed17 100644
--- a/src/win32/msvc-compat.h
+++ b/src/win32/msvc-compat.h
@@ -37,6 +37,15 @@
 /* MSVC doesn't define ssize_t at all */
 typedef SSIZE_T ssize_t;
 
+/* define snprintf using variadic macro support if available */
+#if _MSC_VER >= 1400
+# define snprintf(BUF, SZ, FMT, ...) _snprintf_s(BUF, SZ, _TRUNCATE, FMT, __VA_ARGS__)
+#else
+# define snprintf _snprintf
 #endif
 
+#endif
+
+#define GIT_STDLIB_CALL __cdecl
+
 #endif /* INCLUDE_msvc_compat__ */
diff --git a/src/win32/posix_w32.c b/src/win32/posix_w32.c
index c439dadce..4d56299f7 100644
--- a/src/win32/posix_w32.c
+++ b/src/win32/posix_w32.c
@@ -375,7 +375,8 @@ int p_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr)
 #ifdef _MSC_VER
 	int len;
 
-	if (count == 0 || (len = _vsnprintf(buffer, count, format, argptr)) < 0)
+	if (count == 0 ||
+		(len = _vsnprintf_s(buffer, count, _TRUNCATE, format, argptr)) < 0)
 		return _vscprintf(format, argptr);
 
 	return len;